`
`EXHIBIT
`
`EXHIBIT
`DSS-2003
`
`DSS—2003
`
`

`
`Hartcran House, 231 Kenton Lane, Harrow, HA3 8RP England
`Tel: +44 (0) 20 8909 9595, Fax: +44 (0) 20 8909 2233
`
`Low Duty Cycle?
`Myk Dormer, Senior RF Design Engineer at Radiometrix Ltd
`
`First published in Electronics World magazine, December 2008
`
`The phrase ‘low’ (‘limited’ or ‘restricted’) duty cycle appears in a large num-
`ber of ISM band allocation descriptions, as a favourite method of allowing
`multiple users without calling for the complicated radio hardware that other
`access schemes (multiple channel, spread spectrum or listen before talk)
`require.
`
`The principle behind a low duty cycle system is very simple: by restricting the
`duration and rate of repetition of any one user’s transmissions it becomes statisti-
`cally unlikely that they will coincide (collide) with those of other, similarly limited,
`systems. In practice, the actual restriction is specified as a ‘duty cycle’, usually
`between 0.1% and 10%, depending on the band and the intended usage. In
`layman’s terms this reduces to “you stab the button at random and hope like hell
`that you’re the only one transmitting at that instant”.
`
`There are certain implications that result from this
`type of operation: The transmitter must be designed
`for efficient use of the available time. It must switch
`on and off cleanly (not generating AM splatter, like a
`GSM cellphone does) and the switching needs to be
`as fast as possible to maximise the time allowed for
`data transmission. The data coding must minimise
`the amount of time lost in preamble and synchronis-
`ing sequences, and the overall data rate should be
`as high as practical (within other limitations, such as channel bandwidth).
`
`BiM3B Transceiver
`
`At some point, a collision with another transmission and resulting loss of data is
`inevitable. The overall design of the link must allow for this. In the simplest case,
`this is handled by ‘user feedback re-transmission’ (the light
`doesn’t turn on, so press the button again). Although amusingly simple, this is suffi-
`cient for a large proportion of simple control systems, including almost all car radio-
`keys.
`
`Continued on page 2...
`
`Copyright © 2008 Radiometrix Ltd. All rights reserved.
`
`

`
`Where more sophisticated systems are considered, and data integrity must be
`maintained, then a more effective means of dealing with data loss is needed.
`Sending the same data more than once will reduce (but not eliminate) the
`probability of completely losing a vital piece of information. In such a case, the
`interval between re-transmissions must not be constant (a randomising function is
`required), or there is the risk of another, identical system in close proximity falling
`‘in step’ and the retransmissions always colliding.
`
`Where no data loss is allowable (forexample, in a data download application
`from a data logger), then a transmit/acknowledge protocol must be used. This
`requires transceivers at both ends of the link (opposed to the transmitter/receiver
`pair used by the simpler methods) and the transmission of a ‘data received suc-
`cessfully’ message by the destination end after each burst. The failure to receive
`such a message within a given time window will then cause the originating unit to
`re-send the same data. In this way, the transmission will be repeated until success-
`fully received.
`
`Additionally, once the complexity of a transceiver system has been implemented,
`then the user has the option of using other protocols beyond transmitting at ran-
`dom, as required (such as master/slave polling or master synchronised time slots),
`provided the actual transmission durations are within the spec limits.
`
`European Duty Cycle Limited SRD Bands
`169MHz 0.1% to 10%, depending on the sub-band and transmit power.
`433MHz 10% duty cycle, wideband (> 25kHz channel) 10mW transmitters.
`(no restrictions on sub-1mW units, or narrowband systems).
`868MHz Variously 0.1% to 100%, depending on the sub-band.
`2.45GHz RFID allocation 15%.
`
`See ERC-REC 70-03 for more information.
`
`In addition to the duty cycle limits, this specification also states absolute transmis-
`sion time limits too (otherwise a “10% duty cycleî system could transmit constantly
`for a year and then stay quiet for nine...!)
`
`Maximum total time on in any hour:
`3.6 seconds 0.1% duty cycle
`36 seconds 1 %
`360 seconds 10%
`
`Maximum length of any given transmission:
`0.72 seconds 0.1% duty cycle
`3.6 seconds 1 %
`36 seconds 10%
`
`Minimum ‘off’ time between transmissions:
`0.72 seconds 0.1% duty cycle
`3.6 seconds 1 %
`36 seconds 10%
`Copyright © 2008 Radiometrix Ltd. All rights reserved.
`
`Page 2
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`

`
`About Radiometrix
`
`Established in 1985 and headquartered in London, Radiometrix continues to be
`recognised as the leading global developer of narrow and wideband radio
`communication modules. Our diverse product range is suitable for a wide variety of
`licensed and licence-exempt ISM/SRD wireless applications, and is available
`worldwide through our global sales and distribution network.
`
`For more information on the company, please visit our website:
`www.radiometrix.com
`
`Contact Radiometrix
`Editorial queries can be sent to press@radiometrix.com
`Sales queries can be directed to the sales department: sales@radiometrix.com
`
`Radiometrix Ltd,
`Hartcran House,
`231 Kenton Lane,
`Harrow,
`Middlesex,
`HA3 8RP,
`UK.
`Tel: +44 (0) 208-909-9595
`Fax: +44 (0) 208-909-2233
`
`Limitation of liability
`The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd
`reserves the right to make changes or improvements in the design, specification or manufacture of its sub-
`assembly products without notice. Radiometrix Ltd does not assume any liability arising from the applica-
`tion or use of any product or circuit described herein, nor for any infringements of patents or other rights of
`third parties which may result from the use of its products. This data sheet neither states nor implies war-
`ranty of any kind, including fitness for any particular application. These radio devices may be subject to
`radio interference and may not function as intended if interference is present. We do NOT recommend
`their use for life critical applications. The Intrastat commodity code for all our wireless radio modules is:
`8542 6000.
`
`Copyright © 2008 Radiometrix Ltd. All rights reserved.
`
`Page 3