Multi-Channel-Multi-MAC Model Architecture for … Model Architecture for Multi-Net-Multi-Link Tactical Data Link in NS-2 HE Zhao-xiong, ZHANG Ju, YANG Guang, ZHOU Jing-lun International

Multi-Channel-Multi-MAC Model Architecture for Multi-Net-Multi-Link Tactical Data Link in NS-2 HE Zhao-xiong, ZHANG Ju, YANG Guang, ZHOU Jing-lun

International Journal of Digital Content Technology and its Applications. Volume 5, Number 4, April 2011 Multi-Channel-Multi-MAC Model Architecture for Multi-Net-Multi-Link

Tactical Data Link in NS-2

1HE Zhao-xiong, 2ZHANG Ju, 3YANG Guang, 4ZHOU Jing-lun 1, First Author College of Information System & Management, National University of Defense

Technology, Changsha, China, 410073, [email protected] 2 Fuxin High Technological Academy, Fuxin, China, 123000, [email protected]

3 Department of Management Engineering, Naval University of Engineering, Wuhan, China, 430033, [email protected]

*4, Corresponding Author College of Information System & Management, National University of Defense Technology, Changsha, China, 410073, [email protected]

doi:10.4156/jdcta.vol5.issue4.18

Abstract Because of the coexistence of multiplex tactical data links (TDLs) it is urgent to study the

cooperation of Multi-Net-Multi-Link (MNML) TDL. This paper proposes a Multi-Channel-Multi-MAC (MCMM) model architecture to support MNML TDL simulation. The MCMM model adds several copies of data link layer, network interface and channel which are capable to cover the configurations of multi-channel and multi-MAC. The modification of Network Simulator 2 (NS-2) is presented to achieve the MCMM model. And the validations of the MCMM model is shown by the simulation of MNML TDL, taking the data exchange of Link-11 and Link-16 as an example.

Keywords: Simulation Model, Tactical Data Link, Multi-net, Multi-link

1. Introduction

With the development of tactical data link (TDL), the transmission rate, sys tem capacity, anti-jam, security, survi vability, accurac y, navi gation and ident ification have b een gradual ly im proved. But a new tactical data link can not replace a traditional one immediately. So they will get along with each other for a long time. Additionally different TDL has different features and applications. For example, Link-11 can eas ily sent messages over the h orizon with th e H F f requency, w hile Link-16 has more capacity a nd functions f or multiple ne ts but is a LOS ( Line-Of-Sight) n etwork. This makes t he coexistence of Mu lti-Net-Multi-Link (MNML) TDL to b e a necessity . Because di fferent TDL ha s different communication media and protocols, it is urgency that how to achieve the cooperation[1] and compatibility and to improve the performance of data exchange.

The valid ation of th e coop eration of multi-net an d multi-link i s a co mplex system en gineering related with many factors. And si mulation is the most effective research method for it because of its effectiveness, repeatability, economy, safety and security.

Obviously the U.S. military goes f urther in the field o f TDL modeling and simulation. Man y research institutions and companies (MITRE, SAIC, SRI, MIL3, etc.) have developed a variety of TDL simulation sy stems and co mprehensive application systems, i ncluding NETWA RS, GIES IM, TI MS, SIMNET, EAMLSS, etc, but there are rarely detail reports or documents to release.

From t he scattered documents for publication, r eference [2,3] set up th e structure o f g ateway fo r TDLs. They just give us some principles of TDL modeling and simulation, without the detail design and ach ievement. Reference [4] dev elops a gate way model an d esta blishes an in tegrated s imulation platform to test the cooperation of Link-16 and VHF TDL. But it is based on the ho mogeneous MAC protocol, suc h as L ink-16 a nd VH F TDL w ith T DMA. It can n ot fulfill t he v ariety of TDL with homogeneous protocols, such as Link-11 with Polling and Link-16 with TDMA.

To solve t his problem this p aper takes th e data e xchange betw een Li nk-11 and Lin k-16 as an example, proposes a Multi-Channel-Multi-MAC ( MCMM) model architecture so as to si mulate the MNML TDL. At first the characteristics of Link-11 and Link-16 and the connectivity between them is described. An d then the MCMM model for MN ML T DL is propo sed and the gui des o f Ne twork

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International Journal of Digital Content Technology and its Applications. Volume 5, Number 4, April 2011 Simulator 2 (NS-2) modifications are g iven. Finally the validation of the MCMM m odel is presented by the simulation of MNML TDL. 2. Link-11 and Link-16

As shown in Figure 1, Lin k-11 conn ects multiple plat forms in a net work in wh ich po lling is the common access mode. Usually a certain platform is specified as the network control station (NCS), and the rest serve as t he client. While working the NCS calls th e clients at a pre- order with their address. The cli ent be ing cal led b y t he N CS t urns the stat e from receiving t o sendi ng, and beg ins t o s end messages. When the NCS identifies the stop co de the client sends, it turns the state from receiving to sending and calls the next client. In this way the network runs automatically in circle under the control of the NCS.

Figure 1. Link-11 with Polling

Link-16 is a Co mmunications, Navigation, and Identification (CNI) system. It uses the principle of

frequency hopping TDMA to divide network time and capaci ty into divisions called t ime slots. Each network unit sends messages in its time slots assigned to i ts own, so it no long er needs a NCS[5]. As shown in Figure 2, all units are allocated for a certain number of time s lots for each cycle, in which they emit a string of pulse signal with the pre-assigned frequency; meanwhile the other units receive it. Link-16 can be set to work in multi-net mode when the single-net mode can not meet the requirement of many units, large scale combat or wi de battlefields. In this case Link -16 can be seen as a network with multiple channels and different units can emit signals in different nets with different RF frequency in the same time slots without interference.

Figure 2. Link-16 with TDMA and Multi-Net

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International Journal of Digital Content Technology and its Applications. Volume 5, Number 4, April 2011

After t he U.S. military int roduced Link-16, all o perations h ave bee n turned int o the multi-link operations wi th the co mbination of multiple TDLs, such as Link-11 and Link-16. Operating in such multi-link environment the units have the ability to forward specified messages within different TDLs. Figure 3 shows the typical multi-link TDL structure for Link-11 and Link-16. The FJU (Forwarding JTIDS Unit) is the only unit which works on both links simultaneously. At this time the multi-net and multi-link TDL system become a multi-channel (Link-16 in multi-net mode) and multi-MAC (Polling for Link-11 and TDMA for Link-16) wireless communication network.

Figure 3. Multi-Link joint operation structure for Link-11 and Link-16

3. Multi-Net-Multi-Link TDL structure

As shown in Figure 4-( a) unit s i n Link-11, including t he NCS and the clien ts are u sually s ingle-channel-single-MAC nodes. They share the same physical channel by polling without conflict. Each of them has only one antenna. While working the antenna has been fixed with a certain parameters and it can only transmit in the public physical channel arranged.

As shown in Figure 4-( b) un its i n Link -16 in multi-net mode are ge nerally multi-channel-single-MAC n odes. The n on-interference phys ical chan nels are separ ated by different frequency ho pping pattern. And in TDMA th ere i s n o more th an one un it w hich can tr ansmit in one time slot in o ne channel. Si milarly each un it h as o nly one a ntenna. But the an tenna can ch ange i ts settin gs whil e working, such as frequency for hopping. In this way units can be quickly set to be in different channels in different time slots.

Figure 4. Channel and MAC relationship of MNML TDL

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As described in Sect ion 2 above, FJU is a s pecial unit whi ch co mmunicates in both Link-11 and Link-16. It forwards between them. And it has two antennas, one for Link-11 and one for Link-16. FJU translates Link-11 messages to Link-16 messages following a certain rules, and omits signal to Link-16 by the other antenna, and vice versa. Therefore, FJU is a MCMM unit, which is shown in Figure 4-(c). The Link-11 antenna i n FJ U is with only one chan nel a nd the MAC lay er is p olling. The Lin k-16 antenna in FJU is with multiple ch annels an d th e MAC l ayer i s T DMA. The two a ntennas work simultaneously and can send or receive messages in Link-11 and Link-16 at the same time.

Besides the three types of unit above there is another type of unit, such as the satellite unit, which is used for long-distance relay between different TDLs. Under the normal circumstance it has multiple antennas. And each is wi th one chan nel for a cer tain TDL respectively. So the satellite unit is more than a Single-Channel-Multi-MAC unit, as shown in Figure 4-(d). 4. MCMM model architecture for MNML TDL 4.1. Structure of the model of wireless mobile node in NS-2

NS-2 is a discrete event, packet-level simulator targeted at network research. It has a good opening

and expansibility because of it s open s tructure. I t provides very similar r esults compared to OPNET Modeler [6], enjoys a high international academic reputation, so it is widely used by many researchers around the world [7,8]. Among many wireless network simulation software NS-2 is one of the most commonly used, occupied 44% of the rate [9].

The default built-in model for wireless mobile nodes is used for the simulation of wireless mobile ad ho c network[10]. The model structure is sho wn i n Figure 5 , which consists o f s everal modules, namely, the routing agent (RTagent), logical link sub-layer (LL), address resolution p rotocol (ARP), the interface queue (IFq), medium access control sub-layer (MAC) and the physical channel (Channel).

Figure 5. Structure of the model of wireless mobile node in NS-2

LL and ARP complete the IP address and MAC address translat ion, and they receive the packets

passed down from RTagent and sent to IFq which is with a priority. MAC achieves the MAC protocol, such as I EEE802.11, T DMA and s o on. LL, IFq an d MAC make u p the dat a link lay er. Net work interface (NetIF) simulates the antenna which connects the MAC and Channel. And Channel imitates the physical transmission medium which connects nodes.

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Though NS-2 is do minant s imulation tool of function validation and p erformance evaluation, the model o f w ireless mobile n ode do es n ot s upport multi-channel or multi-MAC. It on ly supp orts the model th at mobile node i s co nnected to a single fixed ch annel. Therefore, in orde r t o si mulate t he MNML TDL extensions of NS-2 are necessary.

4.2. MCMM model architecture for MNML TDL in NS-2

In the extension of NS-2 for multi-channel-multi-MAC simulation, a few researches are worth study.

Reference [11,12] propose the Hyacinth model, but th e MAC protocol and its own routing algorithm are bind t ogether res ulting in the lack of flexibility an d hi erarchical design ideas. Re ference [13 ] proposes the Ramon model which joins a number of data link layer modules that can support single-channel-multi-MAC si mulation. Re ference [14,15] propose the Wei model which can achieve multi-channel-single-MAC s imulation by addi ng several N etIFs betw een MA C and Ch annel. The abo ve three models can not si multaneously s upport multi-channel-multi-MAC si mulation. Re ference [16] presents a VMA model which adds the gateway module, including a data link adapter and several IFqs, between RTagent an d MAC. It achi eves m ulti-channel-multi-MAC si mulation, but it ch anges the overall framework of the communication protocol stack. And what is the most important that it can not separate the multi-link properly and can not work in multiple links simultaneously.

Thus the existing models can not meet the needs for MNML TDL. To sum up, if we want to achieve multi-net T DL, that i s, the u se of multi-channel, we nee d to learn from the Wei model an d make several copies of NetIF and Channel; if we want to meet the needs for multi-link TDL, we should learn from the Ramon model and make several copies of data link layer. Therefore, as shown in Figure 6, the MCMM model proposed in this paper copies multiple sets of data link layer, NetIF and Channel, which is co mpatible with the We i model and Ra mon model. By sett ing t he number o f data li nk layer o r Channel, it can degenerate into the default model of wireless mobile node in NS-2, the Ramon model or the Wei model. Comparing to the VMA m odel, no new gateway is added and it will not affect the existing accepted model of the protocol stack. Also it can work with multiple TDLs simultaneously.

Src/Sink

Rtagent

NetIF

Channel 0

Prop Model

port demux

entry

addr demux255

ip addrdefault

LL

IFq

MAC

LL

IFq

MAC

LL

IFq

MAC

NetIF NetIF

ARP

Channel 1 Channel 2 Figure 6. Structure of the MCMM model in NS-2

By cop ying multiple p arallel da ta li nk l ayer modules multiple ty pes of TDL messages can b e

distinguished wel l, such as the M- series message f or Lin k-11 and the J-s eries message f or Link -16. Different type s o f TDL messages store in diff erent IFq and thus it w ill not caus e compatibility

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International Journal of Digital Content Technology and its Applications. Volume 5, Number 4, April 2011 problems. Different types of TDL messages have to be translated before forwarding to other TDL and this p aper is n ot intent to st udy t he message f ormat translatio n algor ithm a nd w ill not i llustrate it further. Anyone are interested can see reference [17,18]. In addition, a number of parallel independent MAC modules meet the needs for different TDL, such as polling for Link-11 and TDMA for Link-16, by individual configuration. Finally there are also multiple NetIFs, which can simulate the units like FJU or satellite nodes and connect to multiple TDL simultaneously. And each NetIF supports dynamic configuration resulting in the ability to switch several wireless physical channels, which can meet the needs for Link-16 in multi-net mode.

4.3. Connection mode of MCMM models for MNML TDL

The connection mode of MCMM m odels for Link-11 and Link-16 is shown in Figure 7. The left

part is the model for Link-11, which has only one data link layer module for polling, one NetIF for the antenna and one channel naming Channel 0. The right is for Link-16, which has one data link lay er module for TDMA, one NetIF for the antenna and several channels naming Channel 1~n for multi-net. The middle part is for FJU, which has two sets of data link layer modules and two NetIFs. It shares the channels of Link-11 and Link-16 and thus accesses both Link-11 and Link-16.

Figure 7. Typical connection mode of Link-11, FJU and Link-16 for MNML TDL

The messages of Link-16 send from the application layer, pass through the MAC layer for TDMA

and the NetIF, and send to the specified Channel x (x=1, … ,n) according to the type of messages. The FJU, just as the nor mal units of L ink-16, r eceives messages of L ink-16 f rom Channel x, passes the MAC layer for TDMA, and sends to its application layer in the end. If messages are forwarded to Link-11, they hav e to be translat ed in th e application layer. A nd then th e messages ar e se nt through the MAC layer for polling and reach Channel 0 of Link-11. The units of Link-11 receive the messages in Channel 0 and send the m up to the ir application layer. In this way the tr ansmission from Link-16 to Link-11 is over. And vice versa, the transmission from Link-11 to Link-16 is just the similar way.

There are two things that have to be mention in Figure 7. Firstly th e pr opagation model calculates t he s ignal power from the s ource unit to the destination

units in the sam e channel in order to simulate the actual atten uation in wireless p hysical channel[19]. The propagation model relates to the antenna and the physical channel so it has to be set several copies corresponding to the antennas and channels of Link-11 and Link-16.

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Secondly there are several wireless physical channels. All units in Link-11 share one channel, taking 225~400MHz, naming Channel 0 in Figure 7. All units in Link -16 share several channels for multiple nets, t aking 9 60~1215MHz, na ming Ch annel 1 ~n in F igure 7, wh ich can b e s eparated by d ifferent hopping patterns. Thus there is not a share channel for units in Link-11 and Link-16, which can isolate the RF signal s f rom each o ther. The sign als o f Link-11 can not be d irectly listen ed, cap tured or received by the units of Link-16. It has to be forwarded by the intermediate units l ike FJU and vice versa. 5. Simulation and results 5.1. NS-2 software modification

Just as ou r pr evious descr iption o f t he MCMM model, m odifications o f s oftware ar e wit hin the Network Simulator 2 of version 34, NS-2.34, or NS-2 for short in this paper. As NS-2 consists of two major p arts, one i s w ritten in TCL and the other is in C++. TCL i s used for n etwork co nfiguration description and C++ procedure is de veloped f or si mulation processing f unctions. Thereby ach ieving the MCMM model for MNML TDL requires the following modification in both TCL descriptions and C++ procedures.

The guide of NS-2 modifications is given as follows: Adding copies o f data li nk layer modules and NetIFs into ns-mobilenode.tcl. Th is fi le

assembles each entity component into the components, or a module, of MobileNode. The add-interface is changed to define new relations between layers and between sublayer within data link layer. The typical configurations of MCMM are shown in Figure 7. Co ntrol branches are needed to determine which type of configuration to be selected.

Adding th e n umber o f MA Cs control and the number of multiple ch annel c ontrol. Modifications in ns- lib.tcl make multiple channels and multiple MACs available and that in node-config and create-wireless-node have a particular configuration available. Procedures of customizing c haracteristics o f multiple MACs and multi-channel ar e n eeded to s upport t he scenario scripts.

Extending packet he ader. Data link i dentity and chan nel id entity are also recorded in t he packet header.

Adding Data link entity and channel selection algorithm. Because Link-11 and Link-16 usually use si mple flooding and broadcast to send messages, it has to modify the flooding.{h, cc to choose the MA C according to th e ty pe of messages of Link -11 or L ink-16. A lso it h as to modify the mac-tdma.{h, cc} to send messages to the assigned channel in the assigned time slots according to user configurations in Link-16.

Modifying the cmu-trace.{h, cc}. In this way simulation results can show the data link identity and channel identity through which the messages are sent and received.

5.2. MNML TDL simulations

Instead of evaluating the performance of a specific multi-channel MAC pr otocol, the objective o f

this p aper is to propo se the MCMM model, a n ew model for MNML TDL. So we pr esent si mple simulation runni ng results to r eview and a nalyze th e MCMM model va lidity. The i ssues related to NMML TDL simulation are discussed.

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Figure 8. Network throughput of Link-11 and Link-16 for MNML TDL

To demonstrate the MCMM model for MNML and the tactical data exchange between Link-11 and

Link-16 by comparing the various throughput in Link-11 and Link-16. In this simulation there are five units, of which two for clients in Link-11, two for Link-16 and one for both FJU and NCS in Link-11. The two units in Link-16 respectively broadcast periodic surveillance messages working in the multi-net mode. And the messages are f orwarded to Link -11 by FJU. The s imulation result is s hown in Figure 8. Even tho ugh network and cha nnel para meters are s imple an d i deal, the pi cture can on ly demonstrates n etwork throughputs enhan ced w ith multi-channel MAC an d t actical data exchange between Link-11 and Link-16. 6. Conclusion

This p aper proposes a Multi-Channel-Multi-MAC (MCMM) m odel for Multi-Net-Multi-Link (MNML) Tactical Dat a Link (TDL). The MCMM model has the capability to simulate units in T DL which co vers the cases of bo th multiple MACs and multi-channel MACs, such as un its in Lin k-11, units in Lin k-16 and Fo rward JTI DS Uni ts ( FJUs). Gu ides of N S-2 soft ware modifications are also given. Taking the data exchange with Link-11 and Link-1 6 as an exa mple, the si mulation results are analyzed to verif y the MCMM model. The MCMC m odel is f ully con sistent wi th the existing acceptable model of the network protocol stack, can be flexibly used for various networks, and also be used for a variety of TDLs. 7. References [1] Dan XU, Zuo-liang LIU, Feng WANG, “Study of Interconnection for Tactical Data Link”, Space

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Multi-Channel-Multi-MAC Model Architecture for … Model Architecture for Multi-Net-Multi-Link Tactical Data Link in NS-2 HE Zhao-xiong, ZHANG Ju, YANG Guang, ZHOU Jing-lun International