P3 - Portable Deployable Anywhere Communications System

WCDM 2006 DCI Feb-06

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P3 - Portable Deployable Anywhere Communications System

or - Copper Cable Resurrection -

Alec Umansky and Ian Thomas (MAJ Rtrd), February 2006 DEFENCE COMMUNICATIONS INDUSTRY PTY LTD

ABSTRACT This paper examines innovative Australian technology that is setting new standards in field deployed Command and Control communications for military and emergency applications. A new approach to establishing data and voice communications in areas where no other infrastructure may be available will be presented along with cost and functionality comparisons to existing technologies. Early trial results along with latest examples of operational deployments will be presented. The new system �P3� was designed in close consultation with the Australian Army which pioneered its use in most of the recent high profile operations. It therefore closely reflects actual user requirements � namely simplicity of use and effective functionality delivery. This collaborative effort won a prestigious US �Golden Link� Award for technology innovation assisting in the war against terrorism. Based on �off the shelf� technology the new portable field deployable product uses copper wires (DON10 or WD1T) for data and voice links at speeds of up to 8 Mbs over distances of up to 5 miles. Copper cable represents a simple, strong and soldier friendly communications medium. When used with P3s it becomes an effective high bandwidth data and voice infrastructure that is not only cheap and simple to deploy but can be repaired as easily as tying shoelaces together. A number of P3 applications will be overviewed with a focus on its use in disaster recovery. Whether in urban, isolated and extreme terrain, P3s are shown to be an effective means of getting urgent data and voice communications in and out of a disaster site.


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1. Introduction Rapidly deployed, simple to use, effective and reliable communications are vital in disaster recovery and modern military operations. Communications systems must be capable of providing not only voice, data and live images transfer, but must be simple to install, operate and repair. Flexibility of configuration and interoperability are often the additional challenges to overcome. In disaster stricken areas it is the low tech common item that often proves invaluable to people in need of establishing communications. The P3 product was designed from the start to meet these challenges and uses copper cable as its transmission medium. It provides a simple and effective platform for a range of disaster recovery and Defence applications. Based on the �off the shelf� DSL (fast data rates over copper) technology, and with integrated features specified by its direct users, the system meets all of these demands while delivering considerable cost savings without compromising functionality. Designed by Defence Communications Industry Pty Ltd and in close collaboration with RASCs (Royal Australian Signals Corps), the product had proven itself operationally by Australian, New Zealand and British armies � where its primary use is to provide tactical LAN extensions and as a viable alternative to fragile fibre-optic links. Based on DSL technology with specific design adaptations, the product �P3� enables data throughput of 8Mbit/sec over a single pair of copper wires at distances of up to 5 miles. P3�s transmission circuits use rate adaptive, DMT modulation that ensures secure and extremely noise tolerant data links. Each transmission channel outputs less then 3 watts of power that is spread over 300 individual frequency carriers � meaning a balanced transmission with an extremely low noise signature � an inherent advantage where �EW� (electronic warfare) may be a factor. Government level high security can be ensured with the use of network or serial encrypters. P3s allow a wide range of products to run transparently over its copper links: remote sensors, voice telephony, a range of telemetric devices and

video devices - any device with an Ethernet (or an IP) interface. The strength of DSL in defence and disaster recovery applications is that the technology effectively provides the high speed necessary for communications, along with a sturdy infrastructure (copper cable; plain or reinforced). Copper remains the preferred infrastructure in many military and industrial applications and while fibre-optics may offer greater bandwidth, the cable often breaks under strain with its repair being at the very least impractical in the field environment. Wireless technology offers �easy� solutions but only where the radio waves can safely propagate. Copper can be rolled-out rapidly and easily, is soldier friendly and, used with P3s offers fast transmission speeds necessary for field communications. 1.1 DSL Technology Overview

DSL modulation technique takes advantage of the unused bandwidth or frequencies spectrum existing in telephone copper cables. Data rates achievable are in the order of 8Mbit/sec for one direction and 1 Mbit/sec in the other. This modulation technology is asymmetric due to the signal interference arising at such high data rates � hence the acronym ADSL (Asymmetric Digital Subscriber Loop). No new cabling is required, and since ADSL modulation frequencies are above the voice telephony spectrum, it leaves the phone services unaffected. The same telephone (or copper) line is used for both high-speed data applications and standard telephony. ADSL is the ideal medium for fast Internet and LAN extension applications. However, within a traditional Telco framework, it is not used to full advantage, suffering distance limitation (1 to 2 miles subject to line conditions) and speed reduction due to copper plant legacy problems. A review of DSL technology and its modulation technique is at Appendix B.


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1.2 Rationale for the New Product

Many large organisations and companies such as utilities, gas, oil and mining operations already own copper infrastructure either in the ground or in mobile, field deployments. Most cities, and many remote and isolated communities also have copper infrastructure, usually owned by the local telecomms operator. However, this resource has been often under utilised due to the limitations and design restrictions of the standard Telco system. In these communities, deployable packs of copper cables could be easily stored in selected locations (police and fire stations, municipal authorities, school and community centres) � that in time of a disaster and loss of public communications can be rolled out easily and quickly even by inexperienced people and be used as the basis of voice and data infrastructure. The was the rationale for the design of a new product which could utilise this copper infrastructure and be perfectly suitable for rapidly established communications links between individual community groups. An early �proof of concept� prototype � �P4� was designed specifically for the Australian Army to prove that copper cable could be used or resurrected for modern Command and Control (C4I) applications. Successful Army trials of several functioning P4 prototypes proved conclusively the effectiveness of this technology and established grounds for further product development.

2. Portable (RADSL) Systems for Military and Emergency

Applications

2.1 The Concept

Field deployed data applications demand rapidly established communications links of high bandwidth, particularly so in the areas of defence and emergency relief. DSL was identified as one of the best

technologies to cope with this demand in field deployed communications. Based on this conclusion, a new concept of portable RADSL (Rate Adaptive DSL) systems was developed especially suited to military requirements. Portable RADSL Systems provide transparent LAN (10BT Ethernet) extensions over copper wires. Integrated voice telephony operates independently of the data therefore providing an effective 'field telephone' even when data links are down. Specific design features provide flexibility in bandwidth configuration and greater transmission distance than that provided by standard Telco DSL systems. The devices require no additional computers for operation or set up and have integrated, rechargeable battery power.

It should be emphasised that copper, besides being a robust medium is significantly cheaper than fibre-optic based infrastructure. 1 Fibre-optic cable is damaged easily in an operational environment and it is in this domain that the humble copper cable comes into its own. Copper wire if damaged, can be as easily repaired as tying a pair of shoelaces. It can be deployed and retrieved rapidly and in combination with DSL technology, becomes a viable broadband communications medium, especially in areas where radio waves cannot safely propagate. Distances bridged by the new equipment over copper cables are in excess of 3 miles and in some instances had been

1 see 2.5: Cost Comparison - Copper Cable vs Fibre Optic Cable

P3 � Command & Control Deployments


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operationally deployed over 5 miles. Copper cables, plain or reinforced re-emerge as the preferred infrastructure for a range of military, emergency and industrial applications. Including the following: - telemetry, weather monitoring stations and flood warning control systems - Civil Defence & Emergency Services - Police - underground mines - disaster recovery applications (diplomatic missions and embassies) - restoring communications in earthquake zones and to/from refugee camps 2.2 Proof of Concept � the P4

In April 1999 the first portable functioning communications system was produced. P4 was a stand alone system with 4 RADSL channels, integrated telephony and a rechargeable battery. The bandwidth, maximum possible transmission between any two P4s, is automatically set depending on the line condition (using the Rate Adaptive DSL protocol, similar to the way a common telephone modem negotiates its optimal speed) with maximum bandwidth of 8Mbit/sec in one and 1Mbit/sec in the other direction. P4 displays actual line operating parameters on its status display during its operation. Nine P4 functioning prototypes were delivered to Australian Army and successfully trialled during Exercise Phoenix and subsequently used during the East Timor Peacekeeping Mission. See Appendix A for a report extract by Major Ian Thomas and WO2 Peter Thornton of the Australian Army who effectively instigated and promoted DSL technology within the Australian Department of Defence. 2.3 The Current Product � P3

Following the success of the functioning prototype, the product was redesigned to incorporate the latest RADSL technology, higher tolerance electronic components, as well as custom ruggedisation. The optimum number of fully configurable RADSL

channels were determined to be three and telephony functions were designed to combine analogue and digital VoIP modes. The �P3� (Portable 3 channels) is the current portable device and as with P4, requires no external devices to configure or operate - all of the units management is established via the internal microprocessor and keypad. P3s can be set up in a diverse range of configurations, from a simple point to point transparent LAN link to a complex web of units, including full redundancy links. The data repeater mode of operation means a number of P3s can be cascaded together establishing flexible high speed data links over long distances (e.g airport perimeter video monitoring). P3s three transmission channels can be individually configured for �master/slave� operation, thus allowing effective on demand bandwidth management. This simple facilty provides bandwidth where it is required (e.g. a refugee camp sending out bandwidth intensive content of photo or videos of survivers to the disaster management centre and receiving mainly email or text based content, requiring minimal bandwidth.

Six Ethernet (10/100 BaseT) interfaces provide direct connectivity with external LAN networks and a range of �off the shelf� optional accessories such as video camera, sensors, controllers, etc. Any of these devices� functionality can be transparently extended over copper cables.

P3 in ruggedised case and field telephone


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Each P3 unit contains an integrated telephone handset for voice over the same copper wire as for data, independently of the LAN traffic. In the event of LAN failures this will continue to operate as a backup field telephone. Standard PABX lines can be extended by any of the P3 operating channels. VoIP will allow for secure voice communications in a meshed network to any of the other P3 locations. For large scale deployments of P3s, management of the comms network can be done remotely via integrated TCP/IP protocols (e.g. Telnet). The DMT (Discrete multi-tone) modulation, the preferred standard for Defence, provides superior resilience against electrical noise and allows for point to point transmission security (scrambling of data packets). Internal batteries provide backup operation for up to 8 hours under full load conditions and for longer still, if only one or two of the RADSL channels are active. The external AC adaptor can be plugged into power sources such as generator, truck battery or solar panels. This independence of power is particularly relevant in disaster recovery conditions � as often power and other infrastructure is not available for considerable periods. This is the advantage of P3s which are infrastructure independent and extremely simple to use devices. 2.4 Secure Transmission over Copper

P3, with its rate adaptive DMT modulation technology represents highly secure transmission of voice and data over copper in the tactical environment. Digital signal modulation effectively encrypts the data transmission by individually initialising each of the 300 data carriers and testing each for its integrity. At that time, data packets are scrambled across active carriers. The effective result of the data transmission can be equated with that of a �one time pad� � a unique transmission, as data scrambling parameters exist only between any two directly connected P3s. The greater the number of users on any given data link, the greater the scrambling effect. No external device would be capable of �listening in� to the setting up of the transmission parameters process, as the technology provides for two terminal

devices only during the line initialisation. In the event of a copper line being cut, the transmission stops. Similarly, should an external �listening� device be introduced, the initialised transmission parameters will alter and interrupt transmission. The user is able at all times to monitor the line conditions. Government level high security is achieved by the use of IP or serial encryption devices. 2.5 Cost Comparison � Copper Cable vs Fibre Optic Cable and Other Important Factors

Following early equipment trials, Australian Army conducted an assessment of the cost differential between the use of transmission using copper cable compared to fibre optic cable. This is based only on the cost of infrastructure and does not take into account costs of damage and replacement of cables, commonly experienced with fibre optic. Using a variety of scenarios, the following chart shows the exponential cost escalation over distance, and with the addition of backup links. The starkest example of cost escalation is the RTA Trial scenario (blue line), but in all cases it can be seen that the costs of extending copper rises only marginally in contrast to fibre optic cable where the increase is rather more dramatic. Additional factors for consideration are the bulk and weight of FOC, the size of switches and power requirements and complexity of maintenance compared with P3�s portability, simplicity of use and inbuilt telephony features. However, an essential consideration in a disaster recovery situation is not so much the immediate cost of equipment necessary to establish communications, but rather the speed and simplicity of set up and operation. Equally important and not often well considered is reliance on power and other civil infrastructure before disaster relief organisations can consider moving into a disaster area to provide aid. It is at these times that simplicity and ease of P3 deployment really makes sense. With minimal


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FOC - DON10 Cost Comparison Notes : FOC and Sw itches Prices are f rom 1998' P3/P1 and DON10 prices are current

$-

$50,000

$100,000

$150,000

$200,000

$250,000

$300,000

0kms 1kms 2kms 3kms 4kms 5kms 6kms 7kms 8kms 9kms 10kms

RTA Trial FOC Scenario (Sw ch to 3xSw chs over 3KM FOC)

RTA Trial DON10 Scenario (P3 to 3xP1 over 3KM DON10)

Sw itches over 10 KM FOC

Sw itches over 10 KM FOC w ith a backup FOC link

P3 to P3 at 5KM to P3 at 10KM - over DON10

P3 to P3 to P3 (w ith back up DON10 link)

P3 to 3xP3 at 5KM - over DON10

P3 to P3 at 5KM [3xDON10 links] to 3xP3 at 10KM


P3 to P3 at 5 Km to 3xP1s at 10KM - over DON10

FOC - DON10 Cost Comparison Notes : FOC and Sw itches Prices are f rom 1998' P3/P1 and DON10 prices are current

$-

$50,000

$100,000

$150,000

$200,000

$250,000

$300,000

0kms 1kms 2kms 3kms 4kms 5kms 6kms 7kms 8kms 9kms 10kms

RTA Trial FOC Scenario (Sw ch to 3xSw chs over 3KM FOC)

RTA Trial DON10 Scenario (P3 to 3xP1 over 3KM DON10)

Sw itches over 10 KM FOC

Sw itches over 10 KM FOC w ith a backup FOC link

P3 to P3 at 5KM to P3 at 10KM - over DON10

P3 to P3 to P3 (w ith back up DON10 link)


P3 to P3 at 5KM [3xDON10 links] to 3xP3 at 10KM


P3 to P3 at 5 Km to 3xP1s at 10KM - over DON10

Additional Unweighed Factors - FOC Bulk and Weight - FOC propensity for damage - Switches size and power requirements - Switches set-up and maintenance complexity - P3 portability, simplicity of use & telephony features

FOC to Copper Cost Factor ~15

product training communities can quickly and efficiently establish data and voice communications to the �outside� world, in the event of a natural or man-made disaster. Valuable time would not be lost in waiting for the arrival and establishment of infrastructure for aid organisations.

3. Areas of Application

2.6 LAN Extensions for Out of Barracks Communications, Airfield Defence and general adhoc C4I extensions

Australian Defence had identified the need for a solution that allowed its Land Local Area Network (LAN) Communications to be extended to its field deployed logistics units. The in barracks logistics system, the Standard Defence Supply System (SDSS) was to be extended to provide support for its logistics business, whilst being deployed operationally in the field. 2 The resulting deployment of SDSS supported by a stand-alone version of SDSS called FLMS (Field Logistics Management System)

2 Case Study � see References

provides seamless �in and out of barracks� communications.

The extension of the LAN communications was largely made possible with the use of P3 and is now part of Army�s new standard for field deployed communications.

Another important issue addressed by ADF was the need to provide redundant links (backup) for downed fibre optic networks � a regular occurrence in the field. Signallers can easily and cheaply repair copper cable, in sharp contrast to fibre optic cable, resulting in significant cost savings with no loss of capability.

The British Army, in seeking to improve its out of barracks logistics and supply support, (UNICOM OOB) successfully trialled P3 in 2003. P3 is now in service with the British providing remote access and enhancing the capability of the existing UNICOM system.

Connection of high resolution video cameras and sensors provides effective monitoring and surveillance around airfield bases perimeter and similar areas. When coupled with general Command, Control and Communications over the same copper cables P3s offer an extremely simple and flexible platform for Airfield Defence, Military Police and similar applications.


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The Canadian Army has also trialled the product for an innovative �Fire Control� application where the device provides data as well as voice command extensions from a ballistics computer to individual gun positions. Again, the use of copper as the main communications medium is not only significantly cheaper but enhances functionality by providing seamless back up links using the spare P3 transmission channels.

2.7 Civil Defence & Emergency Applications

Communications are of paramount importance in the management of emergency situations. In crises such as fire, flood or explosions, existing communications infrastructures (typically fibre optic networks) are often damaged or destroyed, and an immediate task for emergency response teams will be to enable communications to and from the damage site. There is a further demand for interoperability of equipment between civil emergency response teams and the military.

It is commonly thought that wireless communications will provide an immediate and all encompassing solution. However, in a typical disaster area where no power and other infrastructure may be available it takes considerable time and resources to deliver and setup for wireless. As well, this technology has limitations in propagating in difficult terrain.

In such disaster situations, P3s have a proven functionality. A portable device that is weather proof and independent of power or other infrastructures can be deployed on site instantly. Multiple P3s may be interconnected expediently with field wire (reinforced copper wire) thus creating an independent data and voice network to allow affected communities to exchange video, email, voice and other data sensory information.

An ideal model for emergency preparedness may be for local civil and law authorities, school, community centres and other shelters to stock P3s and field wire. In time of need, localised communications can be established simply and efficiently and then interlinked to the non affected public comms infrastructure.

A complication which arises at the site of major disasters is the sheer number of personnel needing to

communicate with each other. The presence of multiple government agencies and NGOs often results in their duplicating each others efforts and, more frequently, being unable to provide aid and relief due to unavailability of one or the other infrastructure. The P3 system, being compatible with industry data and voice networks as well as with each other, means an agency or NGO can tap in to the P3 communications, from initial through the ongoing stages of operation. The ease with which links are extended between relief camps and actual disaster area of operation, makes it extremely effective to �reach� personnel via voice, data or video, provide full telemedicine capabilities and to offer affected groups communication with the �outside� world. To summarise, in disaster and emergency applications, P3 offers the following capabilities: - rapid restoration of damaged communications links - data recovery after destruction of networks - provision of voice and data in isolated areas such as

refugee camps and rural communities - connection to various sensors to provide, for

example, atmospheric testing, or connected to video camera to provide pictorial site information and other reconnaissance material

��.one of the the most pressing needs emerging in the wake of September 11, is effective communications among civilian and emergency response personnel.� Signal magazine June 2002

2.8 Future Enhancements

The newly emerged ADSL2+ standard will add further distance and bandwidth capability to P3s. Standard Defence batteries will also make the product more versatile. Other new features considered for future product releases are VDSL transmission (up to 52Mbit/sec), as well as radio and fibre-optic modules. In general, a second product generation �MkII� will be a lighter product with broadened applications.


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4. Conclusion

As a result of the past three years, substantiation of the product by ADF and others, it has been determined that a considerable market in both defence and industrial markets exists for this type of specialised product. The decisive factors for this are the dramatic savings in cost, setup and maintenance. Copper continues to be a soldier friendly medium and P3 resurrects its role in meeting today�s communications needs.

While fibre optic will retain its role as the communications backbone, P3 provides Command and Control extensions on the brigade level and below. In its stand-alone operational mode, P3 provides �eyes and ears� through its ability to relay audio-visual and sensors information; while at the same time, being an ideal device for the �business� area of supply, distribution and logistics into the field. The demands of portability, ruggedness and ease of operation and repair, are further met in a fully integrated, stand-alone unit.

Interoperability example of military,

NGOs & government agencies using P3s to

rapidly establish data and voice comms


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5. References:

1. ETSI (European Telecommunications Standards Institute) ADSL standards and specifications: ETSI TS 101 388 and ETR 328

2. ETSI basic ISDN standard : ETSI TS 102 080 3. ETSI basic VDSL standard (incl. key functional

and electrical requirements) : TS 101 270-1 V1.2.1 and TS 101 270-2 V1.1.1

The following references are available from: www.defence-comms.org 4. Australian Army early deployment trial results:

�New Technology - WDD A/TT (Don-10) Network�

5. Case Study SDSS (a complete Filed Deployed Logistics solution)

6. �P3 Transmission over Copper - Security� by A.Umansky 2003

Biography: Alec Umansky began his career in 1981 in the telecommunications industry, with the then Telecom Australia (currently Telstra) in the area of Switching. Following his graduation from RMIT (Royal Melbourne Institute of Technology) where he took a degree in Electronics and Digital Communications, he joined Philips (Public Telecommunications Systems). His work focused on introduction of new fibre-optic transmission technologies (SDH) in Australia, Germany and UK. In addition to his main studies, Alec attained two post-graduate degrees in Advanced Microprocessor Design and Development from RMIT. In March 2000 Alec formed an independent company, Defence Communications Industry specialising in design, development and marketing of communications products for defence and industrial markets. Alec plays guitar, enjoys travelling and is an active AFCEA member (Armed Forces Communications Engineering Association).


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Appendix A: Australian Army Field Trials Report

5.1.1�New Technology - WDD A/TT (Don-10) Network�

Army uses fibre-optic cable to provide a communications infrastructure for logistic support. The fibre optic cable, kevlar-armoured especially for Defence, is an expensive medium and suffers breakages from being caught up in the track link of tanks or broken by forklifts. These accidents, actual events during Exercise Phoenix, normally occur during night under blackout conditions. Although the fibre can be repaired, such repair requires return to base and expensive facilities.

Army traditionally uses Don-10 copper wire strands reinforced with strands of stainless steel wire to carry voice in the field. This cable, capable of withstanding heavy stress, still gets broken but is easily repaired by users. Wire cable deployment is also considerably easier to achieve than laying fibre optic cable. P4 xDSL was employed during Operation Phoenix and Crocodile West to prove an ability to replace fibre optic cable segments with Don-10 on selected long runs.

The following are some first hand impressions and feedback from Army users of the Don-10 technology on Operation Phoenix; �Soldiers understand this and they can fix it� (meaning wire and breaks that occur as opposed to fibre optic cable); �Can I get some more; �This is great�; and �Hey, it works�. Portable xDSL systems provide data rates over copper or steel cables that are acceptable with significantly reduced capital costs. P4 primary application during Operation Phoenix was to enable a transparent LAN extension within a large logistic area, located in the bush near Tindall.

A number of specific future requirements have been discussed. One such special development is a simple back to back xDSL modem, providing the Army with rapid deployment multimedia infrastructure over copper cable. It greatly reduces the cost-per-line factor due to the elimination of the more cumbersome

subrack assembly of a standard system. This technology successfully provided the logistic LAN backbone on Operation Crocodile West, 150 km SW of Tennant Creek, when fibre optic breakages and distance limitations proved difficult to overcome.

The WDD A/TT (Don-10) LAN extensions are robust, cost-effective and well-accepted by soldiers. Tempest-rated within the restricted environment, the solution is now a Defence Infrastructure standard within the strategic environment however it is not yet formally accepted in the tactical arena. end of report

�Crocodile West� Exercises, May-1999 - Proving the �P4� Concept for Tactical LANs


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Appendix B: Standards � Technology Overview & Transmission over Copper Security Aspects

Two main standards bodies in association with the industry are defining DSL standards - ANSI and ETSI. In addition, the ADSL Forum, established in December 1996 actively promotes the ADSL concept, facilitating development of system architectures and protocols. The [email protected] web site offers wide ranging information including links to numerous ADSL manufacturers. DSL has two main modulation techniques: - CAP (Carrier-less Amplitude/Phase Modulation and - DMT (Discrete Multi-tone). CAP is a version of QAM in which incoming data modulates a single carrier that is then transmitted down a telephone line. The carrier itself is suppressed before transmission (it contains no information, and can be reconstructed at the receiver), hence the term �carrier-less� Figure 1. CAP Frequency Transmission Spectrum Figure 2. DMT Frequency Transmission

Spectrum

Figure 1 illustrates the CAP frequency spectrum. It can be seen that voice channel occupies the smallest

part of the spectrum (0..4.3KHz) and can be separated (filtered) from the data frequency spectrum.

Transmission over Copper - Security Aspects

P3 transmission design is based on industry standard DMT (Discrete Multi Tone) Modulation (see above). This modulation ensures optimal transmission for any given condition of a copper link (its quality and thickness, lengths, number of joints, kinks, stretches, as well as adverse weather conditions). DMT modulation allows P3 and/or P1 to establish optimal transmission parameters on any given link of copper cable, reflecting these variable parameters. It is important to note that DMT modulation is established over 250 individual frequency carriers. Each 4.3 kHz carrier (the same as

used for a voice telephone modulation) transmits maximum 64 Kbit/sec of data. Total P3/P1 bandwidth in ideal conditions is 8 Mbit/sec in one direction and 1 Mbit/sec in the other direction (the technology is asymmetrical due to signal interferences arising at these speeds). From the diagram it will be noted that carriers for 8 Mbit/s data stream are separate from 1 Mbit/s carriers. The benefit of this technology is that every frequency carrier is independently tested for �Signal to Noise Ratio� SNR and other data integrity parameters specific (and unique) to the given copper link. The process is called �training� or synchronising the link.


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The positively checked carriers will remain and carry the data traffic. Those carriers that did not check out (whose transmission parameters were of unacceptable level) will be de-activated and not used for the duration of that link. The more de-activated frequency carriers there are after the �training� period the less overall bandwidth between the two P3s or P1s. It should also be noted that �DSL� chipsets continually monitor SNR and Bit Error Rate BER performance of all active frequency carriers. If any of the active carriers return the below threshold result (BER or SNR) the link will resynchronise (re-train) to reflect this change of condition. In practical terms this is likely to occur when

a length of copper is being stretched or damaged or there is an adverse electrical noise present that affects transmission parameters (noisy diesel generator, lightning, EW and similar). Note that these transmission interferences will affect P3/P1 transmission only if they occur at 0 to 1.5MHz spectrum � i.e. active P3/P1 frequency carriers. Frequency noise above 1.5MHz does not affect P3/P1.

DMT modulation provides a dynamic and optimal transmission performance for P3 and P1 in field deployed conditions. It effectively manages and compensates for any adverse noise conditions on the line.

During the line synchronisation phase each of the 250 frequency carriers is tested for Signal to Noise Ratio and Bit Error (SNR and BER). In the event that returned parameters of these tests are below the threshold levels the affected carrier would be deactivated.

• this process effectively adjusts optimal transmission parameters for any given length of copper cable that could be affected by the length, joints, stretches of the copper, atmospheric and other conditions affecting signal transmission

• the Digital Signal Processor (DSP), that is part of all P3 and P1 chipsets, establishes which successfully tested frequency carriers will carry which part of Ethernet data packets

The combined effect of the two processes establishes a once only data protocol between two active P3s or P1s. This data protocol is valid for one given physical link only. Importantly, if anyone or anything �disturbs� the line after the synchronisation phase, the line parameters will change and the devices will stop transmitting. There will be a visual indication to the operator of this disturbance.

No other P3 or P1 device that would be connected to the copper link after the synchronisation phase will be operable � the data protocol will not let it synchronise. The data synchronisation protocol works for two devices on the line only (i.e. any additional device introduced on the line will result in line �disturbance� and consequential stop of transmission.

It is worthwhile to note that all commercially available ADSL line testers and analysers work by substituting one of the ADSL devices on the line � never as an external (third) introduced device. There are no commercially available products that could do this.

In theory it would be possible to design a �spying� ADSL device. The complexity of such a product however, would make it a very unlikely field deployable or portable product. Therefore, given the variable nature of tactical data links it is highly improbable that a �spying� ADSL product would ever come into existence

end of paper

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P3 - Portable Deployable Anywhere Communications System