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A Distributed Low-Redundancy Information Sharing Algorithm in Ad Hoc Networks with Directional Antennas
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Available online at www.sciencedirect.com Procedia Computer Science00 (2018) 000–000 Procedia Computer Science00 (2018) 000–000
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Procedia Computer Science 131 (2018) 1142–1149
8th International Congress of Information and Communication Technology (ICICT-2018) 8th International Congress of Information and Communication Technology (ICICT-2018)
A Distributed Low-Redundancy Information Sharing Algorithm in A Distributed Low-Redundancy Information Sharing Algorithm in Ad Hoc Networks with Directional Antennas Ad Hoc Networks with Directional Antennas Yichen Zhang, Laixian Peng一, Renhui Xu, Jin Li Yichen Zhang, Laixian Peng一, Renhui Xu, Jin Li
College of Communication Engineering, Army Engineering University, Nanjing 210007, China College of Communication Engineering, Army Engineering University, Nanjing 210007, China
Abstract Abstract For sharing information between nodes in directional ad hoc networks with all-to-all broadcast scheme, the network needs an For sharing information between nodes in directional networks all-to-allinbroadcast network needs an efficient solution. To enhance the transmission distancead andhoc suppress the with interference directionalscheme, ad hoc the networks, multi-beam efficient To enhance the transmission distancea and suppresslow-redundancy the interference information in directionalsharing ad hoc algorithm networks, multi-beam adaptive solution. array (MBAA) is proposed. In this paper, distributed (DLRA) is adaptive array is proposed. Inmultiple this paper, a distributed low-redundancy sharing algorithm (DLRA) is designed based (MBAA) on the receiver-oriented access (ROMA). However, ROMAinformation is an efficient scheduling MAC protocol designed based on the receiver-oriented multiple access (ROMA). However, ROMA an efficient MAC protocol that utilizes MBAA, it cannot guarantee the efficiency of information sharing with low is redundancy andscheduling low energy consumption that utilizes MBAA, cannot the efficiency of information sharinginwith redundancy andphase low energy consumption requirements. Aimingit to solveguarantee the problem, our protocol inserts sub-slots the low scheduling access to exchange packet requirements. solve the problem, inserts sub-slots in information the scheduling accessFinally, phase to packet information inAiming order totoreduce redundantour dataprotocol and accelerate the rate of sharing. theexchange performance of information in order with to reduce thebyredundant dataDLRA and accelerate of information the performance of DLRA is compared ROMA simulations. shows a the 20%rate lower redundancy sharing. rate and Finally, lower delay in information DLRA iswhich compared with ROMA byalgorithm simulations. shows a 20% sharing, demonstrates that our is a DLRA valid way to solve the lower similarredundancy problems. rate and lower delay in information sharing, which demonstrates thatby our algorithm is a valid way to solve the similar problems. © 2018 The Authors. Published Elsevier B.V. © 2018 The Published Ltd. © 2018 The Authors. Authors. Published by by Elsevier B.V. Peer-review under responsibility ofElsevier organizing committee of the 8th International Congress of Information and Communication This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review (ICICT-2018). under responsibility of organizing committee of the 8th International Congress of Information and Communication Technology Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Technology (ICICT-2018). Communication Technology. Keywords: ad hoc network, low redundancy, MBAA, scheduling access, information sharing Keywords: ad hoc network, low redundancy, MBAA, scheduling access, information sharing
1. Introduction 1. Introduction Information sharing means that all nodes in the network can share their packets with others and it also known as Information sharing means that all nodesallinnodes the network can share their packets it alsoTherefore, known as all-to-all broadcast. By all-to-all broadcast, in the network eventually havewith otherothers nodes’and packets. all-to-all broadcast. broadcast, all nodes in the network eventually nodes’ packets. Therefore, an effective methodBytoall-to-all schedule the nodes to share information is needed.have Theother above requirements are very an effective method to schedule the nodes to share information is needed. The above requirements are very * Corresponding author. Tel.: +86 17625911006. E-mail address:author. [email protected] * Corresponding Tel.: +86 17625911006. E-mail address: [email protected] 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license https://creativecommons.org/licenses/by-nc-nd/4.0/) 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Communication https://creativecommons.org/licenses/by-nc-nd/4.0/) Technology Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Communication Technology 1877-0509 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Communication Technology 10.1016/j.procs.2018.04.284
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important in some special applications of ad hoc network. For example, in order to strike targets accurately, the data between different weapon platforms in the weapon collaborative data link are required to be shared in real time. Although multi-beam antennas [1] have advantages of increasing network capacity and transmission efficiency, the advantages of multi-beam antennas cannot be exploited without scheduling to avoid the traditional transmission collisions (as shown in Figure 1). ROMA [2] shows a better performance on delay, redundancy rate and throughput than most MAC protocols with MBAA. Therefore, we learn from the basic idea of ROMA protocol in the way of avoiding the transmission collisions and propose the solution to the redundancy problem in the process of information sharing.
Fig. 1. Traditional transmission contention.
There are many researches on MAC protocol in directional selforganized network, however, it has not been specially designed to achieve information sharing. Since we plan to use the directional antennas in the weapon collaborative data link to increase the communication distance and suppress the jamming, we need to make improvements to the existing MAC protocol to accomplish share information. At present, most of the protocols in the traditional one-to-all broadcast in the MAC layer may not be applied to all-to-all broadcast. Especially in the ad hoc network, the one-to-all broadcast has higher delay and more cost and cannot meet the requirements in information sharing. Therefore, the situation is different to all-to-all broadcast and the two methods have the different number of the parallel links. As shown in Figure 2, with the information sharing, each node in the network has more and more data. Due to lack of good mechanisms to avoid redundancy, the probability of redundant data transmission and delay is increasing. In this case, the existing MAC protocol cannot solve the transmission redundancy problem well, resulting in the loss of information validity due to spend a lot of time in sharing information, which may cause unavailable upper-layer applications [1].
Fig. 2. Transmission redundancy in distributed systems.
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Next, Section 2 shows the related work. Section 3 describes the system model. The DLRA is discussed in Section 4. Then, we present our evaluation and results in Section 5. Finally, Section 6 summarizes our conclusion. 2. Related work Directional antennas, which have the potential of space reuse. The purpose of using directional antennas is to increase the radiation power and confidentiality. The main purpose of using directional receive antennas is to increase the signal strength and the anti-interference ability. By directional transmission antennas, the probability of being intercepted, captured and located by the enemy is reduced, the concealment of communication is enhanced, and the anti-interception ability of the network is improved. Meanwhile, to improve the anti-interference ability of the network by changing the direction of the gain when the enemy interferes.
Fig. 3. MAC protocol classification in ad hoc networks with directional antennas.
As shown in Figure 3, the MAC protocol with using directional antennas can be divided into two main mechanisms [3]: one is random access and the other is reservation/scheduling access. In the random access protocol, nodes exchange control information with the destination node before data transmission and generally use the rollback and retransmission mechanisms. The reservation /scheduling access uses partial or whole network topology information to complete access arrangements for all nodes, which are generally used in the TDMA (time division multiple access) mode. It schedules or negotiates a set of schedules for each node or link, which helps nodes or links avoid transmission collision. At the same time, TDMA requires a strict synchronization mechanism. But it’s too difficult for the reservation/scheduling access mechanism to know the whole network topology information in distributed systems [4]. So far, several current methods have been proposed to improve the performance on information sharing in directional selforganized network. There are two main methods called collision recovery and collision prevention [5]. Collision recovery uses retransmission to enhance the broadcast reception ratio. The collision prevention suppresses the influence of the hidden terminal by using the RTS/CTS handshake before transmission. Xu proposes a distributed maximum weight link scheduling algorithm (dMaxQ) [6] for multi-transmit/receive wireless mesh networks, which is a novel queue length-aware distributed link scheduler that only needs one-hop neighbor information ensures distributed link scheduling with high network capacity. The idea of the algorithm is using the sub-slots to convert node’s mode. Wang proposed a reservation mechanism of the MAC protocol called SYNDMAC [7]. The SYN-DMAC algorithm divides the transmission into three phases: the random access phase, the data phase and the ACK phase. The random access phase is used for channel reservation and route discovery (including neighbor discovery). During channel reservation, an improved RTS-CTS-CRTS handshake mechanism based on the use of a new control frame CRTS (confirm RTS) was proposed. After the random access phase, multiple non-collision data transmission take place in parallel.
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Although, these algorithms and methods are still focused on one-to-all broadcast, they could lead to intense competition and oppressive delay if used directly to the all-to-all broadcasts, they inspired us to take advantage of the idea of a handshake process and the mothed to use sub-slots. 3. System model 3.1. Antenna model We use the MBAA to obtain multi-beam forming capability [8]. In our idealized model, the number of beams that can be formed by the MBAA antenna is denoted by M, with side lobe neglected. For the MBAA [1] antenna, it can operate in two modes: directional mode or omni-directional mode. The antenna can detect the exact position and AOA (angle of arrival) of an electromagnetic wave source for the purpose of locating and tracking one-hop neighbors in omni-directional mode and the multi-beam adaptive array can adjust the direction of the beam to any direction transmission or receive in directional mode. As a rule, antennas in different mode have different transmission range. If an antenna in directional mode that it cannot easily obtain the information detected in the omni-directional mode. Because of the half-duplex mode, it can only send or receive packets in the meantime, but cannot send and receive packets at the same time. 3.2. Network model Under the context of weapon collaborative data link, assuming that our network is sparse and treating the network topology as static [9]. All nodes in the network are independent and identical. We do not consider all kinds of interference in the network. All nodes in the same network have a communication radius r and they are strictly synchronized. In this paper, we use frames as the basic structure for carrying different messages in our protocol. To be specific, the frame has control information and different data packet. Before transmission, different nodes exchange frame with control information to reduce the transmission redundancy. 4. A distributed low-redundancy information sharing algorithm 4.1. Time slot structure As shown in Figure 4, we refer to the slot structure scheme of ROMA. ROMA works in two time periods: random access and scheduling access. Each time slot in the random access period is subdivided into smaller time slots, called signal slots. A node transmits a short signal containing topology information through a signal slot [2]. We insert a sub-slot called “Compare” in scheduling access, which is used to exchanged information between the source node and the destination node and got the destination node packet ID [10]. “Compare” sub-slot contains (n+2) micro-time. The “n” is the number of nodes which is covered by the same transmission beam of a source node.
Fig. 4. Time slot structure of DLRA.
In the original time slot structure, the source node randomly sends packets to the destination node from a predetermined time slot from 1 to Tsched therefore that it cannot guarantee the destination node obtains the packet which it wants. More and more repeated packet transmission causes the node's packet redundancy rate to become higher and higher. According to what has been discussed above, in DLRA protocol, we use the “Compare” sub-slot to give source and destination nodes an opportunity to discuss which packets should be transmitted.
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4.2. Frame format Depicted by Figure 5, the frame format of “Tx1”, “Tx2” and “Rx” (represents Rx1 to Rxn) micro-slots are divided into the same four parts: they contain the frame type, sender’s address, receiver’s address and own packet ID. The frame format of Ttr sub-slot contains three parts: frame type, receiver’s address and transmitting packet ID.
Fig. 5. Frame format of DLRA.
4.3. Specific scheduling mechanism Before elaborating DLRA algorithm, we need to pay attention to two points: first, ROMA algorithm does not limit the receivers covered by the same transmission beam. Second, in the Rx time slot, only one receiver feedbacks the information, while the other receiver keeping silent. As Figure 6 illustrates, we use ROMA algorithm to decide the mode of a node and its one-hop neighbors, and their beams point the to each other first (Figure 6 (a)). Next, in Tx1 micro-slot, sender transmits Tx frame with packet ID in “DataID” and receiver’s address in “DesID” to receivers (Figure 6 (b)). And node 1 has a unique receiver’s address in “DesID” for each transmission beam. Because the number of nodes covered by the transmission beam of node 1 is three, therefore we need three Rx micro-slots (Rx1, Rx2, Rx3). Node 2, 3 and 4 both can receive the frame sent by node 1 containing the destination node ID. In Rx1 micro-slot, the destination node feedbacks its packet ID to node 1 first, and the rest nodes feedback their own packet ID to node 1 in Rx2 and Rx3 according to the order of their node numbers (Figure 6 (c) (d) (e)).
Fig. 6. Expected scheduling and information sharing process of DLRA.
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When the Rx time slot ends, node 1 receives the packet ID that the receivers need most, and then time slot enters the Tx2. In the Tx2 time slot, node 1 sends to node 2, 3 and 4 a frame containing the packet ID to be transmitted based on the received feedback information. After receiving the frame of node 1, the nodes 2, 3 and 4 are compared their own packet ID with the packet ID which will be transmitted by node 1. If their ID number are duplicated, the receiver turns off the reception beam and avoids redundant data reception; If it is not repeated, the receiver prepares to receive the new packet (Figure 6 (f)). Next, in Ttr time slot, data transmission starts. Silent nodes in the Rx time slot can get the Ttr frame. Such as node 2 and 3 receive the packet which ID is 1, because of the repeated packet ID, node 4 refuses to receive the packet sent by node 1 (Figure 6 (g)). After above scheduling process, the network information sharing is completed (Figure 6 (h)). 5. Performance evaluation 5.1. Simulation assumption In this paper, we use OPNET 14.5 to observe the performance of DLRA on information sharing in ad hoc network. We generate the multi-hop networks by randomly placing 16, 25, 36, 49, 64 and 81 nodes within a square plane of 900×900, 1000×1000, 1100×1100, 1300×1300, 1400×1400 and 1500×1500 m2 and the antenna transmission ranges are set to 300 meters. Only roughly static and synchronized networks are considered in our simulations. Before the simulations, we assumed that all nodes know their two-hop neighbor information. The simulation is operated by the following assumptions: The width of beam of directional antenna is 30o, and the maximal number of active antenna beams is 4. Side lobes are neglected for simplicity. The bandwidth of the radio channel is 2 Mbps. The bandwidths of all links are assigned 1 in all simulations for simplicity. Each node has a packet size of 1KB and the Tx and Rx frame is 0.1KB. Micro-slots Tx and Rx both last for 1ms. The Ttr lasts for 8ms. Therefore, the time slot in DLRA is longer than what in the original ROMA. 5.2. Result analysis Figure 7 shows the time delay of DLRA and ROMA to complete information sharing with a different number of nodes. Although the time slots in DLRA protocol are longer than the time slots in ROMA, figure 7 proves that the DLRA spends much less time than ROMA in network information sharing. With the number of nodes increasing, ROMA's time cost increases rapidly while the DLRA protocol maintains a relatively low growth up rate.
Fig. 7. The time cost of DLRA and ROMA for information sharing.
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Figure 8 shows the data statistics for DLRA and ROMA of information sharing with different nodes. The four bar charts, from left to right, representing: the sum of the received data in ROMA, the sum of the redundant data in ROMA, the sum of the received data in DLRA and the sum of the redundant data in DLRA. The sum of the data received by above different protocols at the same number of nodes in identical simulation scenario is almost the same, but it can be seen that under the DLRA protocol, the redundant data in network information sharing is greatly reduced compared to the ROMA protocol. Because the sender and receiver in the intercommunicating of DLRA can select packet by comparison, without such a comparison mechanism in ROMA, the data transmission is random.
Fig. 8. The proportion of redundant data of the DLRA and ROMA.
Figure 9 shows redundancy rate of DLRA and ROMA to complete information sharing. Compared with ROMA, DLRA increases the number of valid data, meanwhile reduces the amount of redundant data. Therefore, it can be seen from the figure that the redundancy rate of the DLRA is reduced by about 20%.
Fig. 9. The redundancy rate of the DLRA and ROMA.
Because the DLRA is improved based on ROMA, the main idea of this protocol is to add sub-slots in the scheduling access phase of the original ROMA. Although this method has a good effect, it inadvertently complicates the protocol. How to additionally decrease the redundant data in the proportion of the total data, and how to further reducing the delay and other issues need to be studied in the future.
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6. Conclusion In this paper, we propose a modified MAC protocol based on a non-collision scheduling protocol to enhance the performance of information sharing in directional ad hoc networks with MBAA antennas. By exchanging packet ID in sub-slots, redundant data can be significantly reduced in information sharing while our protocol also reduces time cost and energy consumption. Using OPNET 14.5, the simulation shows that our method in this paper can improve the performance of information sharing and provide a way to solve the similar problems. However, the proportion of redundant data is still relatively large. A more efficient algorithm should be researched for the performance of information sharing. Acknowledgements We like to thank the anonymous reviewers for their constructive feedback, which have improved the presentation of this paper significantly. References 1. Bazan and M. Jaseemuddin, "A Survey On MAC Protocols for Wireless Adhoc Networks with Beamforming Antennas," in IEEE Communications Surveys & Tutorials, vol. 14, no. 2, pp. 216-239, Second Quarter 2012. 2. L. Bao and J.J. Garcia-Luna-Aceves, “Receiver-oriented multiple access in ad hoc networks with directional antennas”, Wireless Networks, vol. 11, no. 1-2, pp. 67-79, 2005 3. H. Dai, K. Ng, M. Li, M. Wu, “An overview of using directional antennas in wireless networks,” International Journal of Communication Systems, vol. 26, no. 4, pp. 413–448, 2013 4. P. Duan, L. Peng, R. Xu, J. Zhang, J. Zhu, “An all-to-all broadcast protocol for variable packet sizes using directional antennas,” Wireless and Optical Communication Conference (WOCC) 2016 25th, pp. 1-5, 2016, ISSN 2379-1276. 5. Xiaofeng Lu, Towsley Don, Lio Pietro and Xiong Zhang, “An Adaptive Directional MAC Protocol for Ad Hoc Networks Using Directional Antennas,” Science China Information Sciences, vol. 55, no. 6, pp.1360–1371, 2012. 6. Y. Xu, K. W. Chin, R. Raad and S. Soh, "A Novel Distributed Max-Weight Link Scheduler for Multi-Transmit/Receive Wireless Mesh Networks," in IEEE Transactions on Vehicular Technology, vol. 65, no. 11, pp. 9345-9357, Nov. 2016. 7. J. Wang, H. Zhai, P. Li, Y. Fang, D. Wu, “Directional medium access control for ad hoc networks”, Wireless Networks, vol. 15, no. 8, pp. 1059-1073, 2009 8. K. Chin, “A new link scheduling algorithm for concurrent Tx/Rx wireless mesh networks,” in Proc. IEEE ICC, Beijing, China, May 2008, pp. 3050–3054. 9. Mo Li, Limin Yang, Youyun Xu and Kui Xu, “MAC Layer Broadcast Algorithm in Ad Hoc Networks with Directional Antennas,” WPMC 2011 14th, International Symposium, pp.1–5,2011. 10. P. Duan, L. Peng, R. Xu, W. Zhao and C. Tian, “An all-to-all broadcasting protocol using directional antennas in multi-hop wireless networks,” 2015 International Conference on Wireless Communications & Signal Processing (WCSP), Nanjing, 2015, pp. 1-6.
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Available online at www.sciencedirect.com Procedia Computer Science00 (2018) 000–000 Procedia Computer Science00 (2018) 000–000
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Procedia Computer Science 131 (2018) 1142–1149
8th International Congress of Information and Communication Technology (ICICT-2018) 8th International Congress of Information and Communication Technology (ICICT-2018)
A Distributed Low-Redundancy Information Sharing Algorithm in A Distributed Low-Redundancy Information Sharing Algorithm in Ad Hoc Networks with Directional Antennas Ad Hoc Networks with Directional Antennas Yichen Zhang, Laixian Peng一, Renhui Xu, Jin Li Yichen Zhang, Laixian Peng一, Renhui Xu, Jin Li
College of Communication Engineering, Army Engineering University, Nanjing 210007, China College of Communication Engineering, Army Engineering University, Nanjing 210007, China
Abstract Abstract For sharing information between nodes in directional ad hoc networks with all-to-all broadcast scheme, the network needs an For sharing information between nodes in directional networks all-to-allinbroadcast network needs an efficient solution. To enhance the transmission distancead andhoc suppress the with interference directionalscheme, ad hoc the networks, multi-beam efficient To enhance the transmission distancea and suppresslow-redundancy the interference information in directionalsharing ad hoc algorithm networks, multi-beam adaptive solution. array (MBAA) is proposed. In this paper, distributed (DLRA) is adaptive array is proposed. Inmultiple this paper, a distributed low-redundancy sharing algorithm (DLRA) is designed based (MBAA) on the receiver-oriented access (ROMA). However, ROMAinformation is an efficient scheduling MAC protocol designed based on the receiver-oriented multiple access (ROMA). However, ROMA an efficient MAC protocol that utilizes MBAA, it cannot guarantee the efficiency of information sharing with low is redundancy andscheduling low energy consumption that utilizes MBAA, cannot the efficiency of information sharinginwith redundancy andphase low energy consumption requirements. Aimingit to solveguarantee the problem, our protocol inserts sub-slots the low scheduling access to exchange packet requirements. solve the problem, inserts sub-slots in information the scheduling accessFinally, phase to packet information inAiming order totoreduce redundantour dataprotocol and accelerate the rate of sharing. theexchange performance of information in order with to reduce thebyredundant dataDLRA and accelerate of information the performance of DLRA is compared ROMA simulations. shows a the 20%rate lower redundancy sharing. rate and Finally, lower delay in information DLRA iswhich compared with ROMA byalgorithm simulations. shows a 20% sharing, demonstrates that our is a DLRA valid way to solve the lower similarredundancy problems. rate and lower delay in information sharing, which demonstrates thatby our algorithm is a valid way to solve the similar problems. © 2018 The Authors. Published Elsevier B.V. © 2018 The Published Ltd. © 2018 The Authors. Authors. Published by by Elsevier B.V. Peer-review under responsibility ofElsevier organizing committee of the 8th International Congress of Information and Communication This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review (ICICT-2018). under responsibility of organizing committee of the 8th International Congress of Information and Communication Technology Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Technology (ICICT-2018). Communication Technology. Keywords: ad hoc network, low redundancy, MBAA, scheduling access, information sharing Keywords: ad hoc network, low redundancy, MBAA, scheduling access, information sharing
1. Introduction 1. Introduction Information sharing means that all nodes in the network can share their packets with others and it also known as Information sharing means that all nodesallinnodes the network can share their packets it alsoTherefore, known as all-to-all broadcast. By all-to-all broadcast, in the network eventually havewith otherothers nodes’and packets. all-to-all broadcast. broadcast, all nodes in the network eventually nodes’ packets. Therefore, an effective methodBytoall-to-all schedule the nodes to share information is needed.have Theother above requirements are very an effective method to schedule the nodes to share information is needed. The above requirements are very * Corresponding author. Tel.: +86 17625911006. E-mail address:author. [email protected] * Corresponding Tel.: +86 17625911006. E-mail address: [email protected] 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license https://creativecommons.org/licenses/by-nc-nd/4.0/) 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Communication https://creativecommons.org/licenses/by-nc-nd/4.0/) Technology Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Communication Technology 1877-0509 © 2018 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0/) Selection and peer-review under responsibility of the scientific committee of the 8th International Congress of Information and Communication Technology 10.1016/j.procs.2018.04.284
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important in some special applications of ad hoc network. For example, in order to strike targets accurately, the data between different weapon platforms in the weapon collaborative data link are required to be shared in real time. Although multi-beam antennas [1] have advantages of increasing network capacity and transmission efficiency, the advantages of multi-beam antennas cannot be exploited without scheduling to avoid the traditional transmission collisions (as shown in Figure 1). ROMA [2] shows a better performance on delay, redundancy rate and throughput than most MAC protocols with MBAA. Therefore, we learn from the basic idea of ROMA protocol in the way of avoiding the transmission collisions and propose the solution to the redundancy problem in the process of information sharing.
Fig. 1. Traditional transmission contention.
There are many researches on MAC protocol in directional selforganized network, however, it has not been specially designed to achieve information sharing. Since we plan to use the directional antennas in the weapon collaborative data link to increase the communication distance and suppress the jamming, we need to make improvements to the existing MAC protocol to accomplish share information. At present, most of the protocols in the traditional one-to-all broadcast in the MAC layer may not be applied to all-to-all broadcast. Especially in the ad hoc network, the one-to-all broadcast has higher delay and more cost and cannot meet the requirements in information sharing. Therefore, the situation is different to all-to-all broadcast and the two methods have the different number of the parallel links. As shown in Figure 2, with the information sharing, each node in the network has more and more data. Due to lack of good mechanisms to avoid redundancy, the probability of redundant data transmission and delay is increasing. In this case, the existing MAC protocol cannot solve the transmission redundancy problem well, resulting in the loss of information validity due to spend a lot of time in sharing information, which may cause unavailable upper-layer applications [1].
Fig. 2. Transmission redundancy in distributed systems.
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Next, Section 2 shows the related work. Section 3 describes the system model. The DLRA is discussed in Section 4. Then, we present our evaluation and results in Section 5. Finally, Section 6 summarizes our conclusion. 2. Related work Directional antennas, which have the potential of space reuse. The purpose of using directional antennas is to increase the radiation power and confidentiality. The main purpose of using directional receive antennas is to increase the signal strength and the anti-interference ability. By directional transmission antennas, the probability of being intercepted, captured and located by the enemy is reduced, the concealment of communication is enhanced, and the anti-interception ability of the network is improved. Meanwhile, to improve the anti-interference ability of the network by changing the direction of the gain when the enemy interferes.
Fig. 3. MAC protocol classification in ad hoc networks with directional antennas.
As shown in Figure 3, the MAC protocol with using directional antennas can be divided into two main mechanisms [3]: one is random access and the other is reservation/scheduling access. In the random access protocol, nodes exchange control information with the destination node before data transmission and generally use the rollback and retransmission mechanisms. The reservation /scheduling access uses partial or whole network topology information to complete access arrangements for all nodes, which are generally used in the TDMA (time division multiple access) mode. It schedules or negotiates a set of schedules for each node or link, which helps nodes or links avoid transmission collision. At the same time, TDMA requires a strict synchronization mechanism. But it’s too difficult for the reservation/scheduling access mechanism to know the whole network topology information in distributed systems [4]. So far, several current methods have been proposed to improve the performance on information sharing in directional selforganized network. There are two main methods called collision recovery and collision prevention [5]. Collision recovery uses retransmission to enhance the broadcast reception ratio. The collision prevention suppresses the influence of the hidden terminal by using the RTS/CTS handshake before transmission. Xu proposes a distributed maximum weight link scheduling algorithm (dMaxQ) [6] for multi-transmit/receive wireless mesh networks, which is a novel queue length-aware distributed link scheduler that only needs one-hop neighbor information ensures distributed link scheduling with high network capacity. The idea of the algorithm is using the sub-slots to convert node’s mode. Wang proposed a reservation mechanism of the MAC protocol called SYNDMAC [7]. The SYN-DMAC algorithm divides the transmission into three phases: the random access phase, the data phase and the ACK phase. The random access phase is used for channel reservation and route discovery (including neighbor discovery). During channel reservation, an improved RTS-CTS-CRTS handshake mechanism based on the use of a new control frame CRTS (confirm RTS) was proposed. After the random access phase, multiple non-collision data transmission take place in parallel.
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Although, these algorithms and methods are still focused on one-to-all broadcast, they could lead to intense competition and oppressive delay if used directly to the all-to-all broadcasts, they inspired us to take advantage of the idea of a handshake process and the mothed to use sub-slots. 3. System model 3.1. Antenna model We use the MBAA to obtain multi-beam forming capability [8]. In our idealized model, the number of beams that can be formed by the MBAA antenna is denoted by M, with side lobe neglected. For the MBAA [1] antenna, it can operate in two modes: directional mode or omni-directional mode. The antenna can detect the exact position and AOA (angle of arrival) of an electromagnetic wave source for the purpose of locating and tracking one-hop neighbors in omni-directional mode and the multi-beam adaptive array can adjust the direction of the beam to any direction transmission or receive in directional mode. As a rule, antennas in different mode have different transmission range. If an antenna in directional mode that it cannot easily obtain the information detected in the omni-directional mode. Because of the half-duplex mode, it can only send or receive packets in the meantime, but cannot send and receive packets at the same time. 3.2. Network model Under the context of weapon collaborative data link, assuming that our network is sparse and treating the network topology as static [9]. All nodes in the network are independent and identical. We do not consider all kinds of interference in the network. All nodes in the same network have a communication radius r and they are strictly synchronized. In this paper, we use frames as the basic structure for carrying different messages in our protocol. To be specific, the frame has control information and different data packet. Before transmission, different nodes exchange frame with control information to reduce the transmission redundancy. 4. A distributed low-redundancy information sharing algorithm 4.1. Time slot structure As shown in Figure 4, we refer to the slot structure scheme of ROMA. ROMA works in two time periods: random access and scheduling access. Each time slot in the random access period is subdivided into smaller time slots, called signal slots. A node transmits a short signal containing topology information through a signal slot [2]. We insert a sub-slot called “Compare” in scheduling access, which is used to exchanged information between the source node and the destination node and got the destination node packet ID [10]. “Compare” sub-slot contains (n+2) micro-time. The “n” is the number of nodes which is covered by the same transmission beam of a source node.
Fig. 4. Time slot structure of DLRA.
In the original time slot structure, the source node randomly sends packets to the destination node from a predetermined time slot from 1 to Tsched therefore that it cannot guarantee the destination node obtains the packet which it wants. More and more repeated packet transmission causes the node's packet redundancy rate to become higher and higher. According to what has been discussed above, in DLRA protocol, we use the “Compare” sub-slot to give source and destination nodes an opportunity to discuss which packets should be transmitted.
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4.2. Frame format Depicted by Figure 5, the frame format of “Tx1”, “Tx2” and “Rx” (represents Rx1 to Rxn) micro-slots are divided into the same four parts: they contain the frame type, sender’s address, receiver’s address and own packet ID. The frame format of Ttr sub-slot contains three parts: frame type, receiver’s address and transmitting packet ID.
Fig. 5. Frame format of DLRA.
4.3. Specific scheduling mechanism Before elaborating DLRA algorithm, we need to pay attention to two points: first, ROMA algorithm does not limit the receivers covered by the same transmission beam. Second, in the Rx time slot, only one receiver feedbacks the information, while the other receiver keeping silent. As Figure 6 illustrates, we use ROMA algorithm to decide the mode of a node and its one-hop neighbors, and their beams point the to each other first (Figure 6 (a)). Next, in Tx1 micro-slot, sender transmits Tx frame with packet ID in “DataID” and receiver’s address in “DesID” to receivers (Figure 6 (b)). And node 1 has a unique receiver’s address in “DesID” for each transmission beam. Because the number of nodes covered by the transmission beam of node 1 is three, therefore we need three Rx micro-slots (Rx1, Rx2, Rx3). Node 2, 3 and 4 both can receive the frame sent by node 1 containing the destination node ID. In Rx1 micro-slot, the destination node feedbacks its packet ID to node 1 first, and the rest nodes feedback their own packet ID to node 1 in Rx2 and Rx3 according to the order of their node numbers (Figure 6 (c) (d) (e)).
Fig. 6. Expected scheduling and information sharing process of DLRA.
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When the Rx time slot ends, node 1 receives the packet ID that the receivers need most, and then time slot enters the Tx2. In the Tx2 time slot, node 1 sends to node 2, 3 and 4 a frame containing the packet ID to be transmitted based on the received feedback information. After receiving the frame of node 1, the nodes 2, 3 and 4 are compared their own packet ID with the packet ID which will be transmitted by node 1. If their ID number are duplicated, the receiver turns off the reception beam and avoids redundant data reception; If it is not repeated, the receiver prepares to receive the new packet (Figure 6 (f)). Next, in Ttr time slot, data transmission starts. Silent nodes in the Rx time slot can get the Ttr frame. Such as node 2 and 3 receive the packet which ID is 1, because of the repeated packet ID, node 4 refuses to receive the packet sent by node 1 (Figure 6 (g)). After above scheduling process, the network information sharing is completed (Figure 6 (h)). 5. Performance evaluation 5.1. Simulation assumption In this paper, we use OPNET 14.5 to observe the performance of DLRA on information sharing in ad hoc network. We generate the multi-hop networks by randomly placing 16, 25, 36, 49, 64 and 81 nodes within a square plane of 900×900, 1000×1000, 1100×1100, 1300×1300, 1400×1400 and 1500×1500 m2 and the antenna transmission ranges are set to 300 meters. Only roughly static and synchronized networks are considered in our simulations. Before the simulations, we assumed that all nodes know their two-hop neighbor information. The simulation is operated by the following assumptions: The width of beam of directional antenna is 30o, and the maximal number of active antenna beams is 4. Side lobes are neglected for simplicity. The bandwidth of the radio channel is 2 Mbps. The bandwidths of all links are assigned 1 in all simulations for simplicity. Each node has a packet size of 1KB and the Tx and Rx frame is 0.1KB. Micro-slots Tx and Rx both last for 1ms. The Ttr lasts for 8ms. Therefore, the time slot in DLRA is longer than what in the original ROMA. 5.2. Result analysis Figure 7 shows the time delay of DLRA and ROMA to complete information sharing with a different number of nodes. Although the time slots in DLRA protocol are longer than the time slots in ROMA, figure 7 proves that the DLRA spends much less time than ROMA in network information sharing. With the number of nodes increasing, ROMA's time cost increases rapidly while the DLRA protocol maintains a relatively low growth up rate.
Fig. 7. The time cost of DLRA and ROMA for information sharing.
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Figure 8 shows the data statistics for DLRA and ROMA of information sharing with different nodes. The four bar charts, from left to right, representing: the sum of the received data in ROMA, the sum of the redundant data in ROMA, the sum of the received data in DLRA and the sum of the redundant data in DLRA. The sum of the data received by above different protocols at the same number of nodes in identical simulation scenario is almost the same, but it can be seen that under the DLRA protocol, the redundant data in network information sharing is greatly reduced compared to the ROMA protocol. Because the sender and receiver in the intercommunicating of DLRA can select packet by comparison, without such a comparison mechanism in ROMA, the data transmission is random.
Fig. 8. The proportion of redundant data of the DLRA and ROMA.
Figure 9 shows redundancy rate of DLRA and ROMA to complete information sharing. Compared with ROMA, DLRA increases the number of valid data, meanwhile reduces the amount of redundant data. Therefore, it can be seen from the figure that the redundancy rate of the DLRA is reduced by about 20%.
Fig. 9. The redundancy rate of the DLRA and ROMA.
Because the DLRA is improved based on ROMA, the main idea of this protocol is to add sub-slots in the scheduling access phase of the original ROMA. Although this method has a good effect, it inadvertently complicates the protocol. How to additionally decrease the redundant data in the proportion of the total data, and how to further reducing the delay and other issues need to be studied in the future.
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6. Conclusion In this paper, we propose a modified MAC protocol based on a non-collision scheduling protocol to enhance the performance of information sharing in directional ad hoc networks with MBAA antennas. By exchanging packet ID in sub-slots, redundant data can be significantly reduced in information sharing while our protocol also reduces time cost and energy consumption. Using OPNET 14.5, the simulation shows that our method in this paper can improve the performance of information sharing and provide a way to solve the similar problems. However, the proportion of redundant data is still relatively large. A more efficient algorithm should be researched for the performance of information sharing. Acknowledgements We like to thank the anonymous reviewers for their constructive feedback, which have improved the presentation of this paper significantly. References 1. Bazan and M. Jaseemuddin, "A Survey On MAC Protocols for Wireless Adhoc Networks with Beamforming Antennas," in IEEE Communications Surveys & Tutorials, vol. 14, no. 2, pp. 216-239, Second Quarter 2012. 2. L. Bao and J.J. Garcia-Luna-Aceves, “Receiver-oriented multiple access in ad hoc networks with directional antennas”, Wireless Networks, vol. 11, no. 1-2, pp. 67-79, 2005 3. H. Dai, K. Ng, M. Li, M. Wu, “An overview of using directional antennas in wireless networks,” International Journal of Communication Systems, vol. 26, no. 4, pp. 413–448, 2013 4. P. Duan, L. Peng, R. Xu, J. Zhang, J. Zhu, “An all-to-all broadcast protocol for variable packet sizes using directional antennas,” Wireless and Optical Communication Conference (WOCC) 2016 25th, pp. 1-5, 2016, ISSN 2379-1276. 5. Xiaofeng Lu, Towsley Don, Lio Pietro and Xiong Zhang, “An Adaptive Directional MAC Protocol for Ad Hoc Networks Using Directional Antennas,” Science China Information Sciences, vol. 55, no. 6, pp.1360–1371, 2012. 6. Y. Xu, K. W. Chin, R. Raad and S. Soh, "A Novel Distributed Max-Weight Link Scheduler for Multi-Transmit/Receive Wireless Mesh Networks," in IEEE Transactions on Vehicular Technology, vol. 65, no. 11, pp. 9345-9357, Nov. 2016. 7. J. Wang, H. Zhai, P. Li, Y. Fang, D. Wu, “Directional medium access control for ad hoc networks”, Wireless Networks, vol. 15, no. 8, pp. 1059-1073, 2009 8. K. Chin, “A new link scheduling algorithm for concurrent Tx/Rx wireless mesh networks,” in Proc. IEEE ICC, Beijing, China, May 2008, pp. 3050–3054. 9. Mo Li, Limin Yang, Youyun Xu and Kui Xu, “MAC Layer Broadcast Algorithm in Ad Hoc Networks with Directional Antennas,” WPMC 2011 14th, International Symposium, pp.1–5,2011. 10. P. Duan, L. Peng, R. Xu, W. Zhao and C. Tian, “An all-to-all broadcasting protocol using directional antennas in multi-hop wireless networks,” 2015 International Conference on Wireless Communications & Signal Processing (WCSP), Nanjing, 2015, pp. 1-6.