`THE NEW ADSL STANDARDS
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`March 25, 2003
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`Dish
`Exhibit 1047, Page 1
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`ADSL2 AND ADSL2plus - THE NEW ADSL STANDARDS
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`In July 2002, the ITU completed G.992.3 and G.992.41, two new standards for ADSL
`technology collectively called “ADSL2”. In January 2003, as users of ADSL chipsets
`based on the first generation of ADSL standards passed the 30-million mark, G.992.5
`officially joined the ADSL2 family as ADSL2plus, (or ADSL2+ as it is commonly known).
`Several other features and improvements were also incorporated in the form of new
`Annexes.
`Carriers, service providers, and subscribers have played a key role in the completion of
`ADSL2, having provided valuable feedback from the field that the ITU in turn
`incorporated into the standards in the form of new features and performance
`improvements. As a result, ADSL2 will be more user-friendly to subscribers and more
`profitable to carriers, and promises to continue the great success of ADSL through the
`rest of the decade.
`ADSL2 (ITU G.992.3 and G.992.4) adds new features and functionality targeted at
`improving performance and interoperability, and adds support for new applications,
`services, and deployment scenarios. Among the changes are improvements in data rate
`and reach performance, rate adaptation, diagnostics, and stand-by mode, to name a
`few.
`ADSL2plus (ITU G.992.5) doubles the bandwidth used for downstream data
`transmission, effectively doubling the maximum downstream data rates, and achieving
`rates of 20 Mbps on phone lines as long at 5,000 feet. ADSL2plus solutions will most
`commonly be multimodal, interoperating with ADSL and ADSL2, as well as with
`ADSL2plus chipsets. More detail about ADSL2plus is included later in this paper.
`ADSL2plus will enable service providers to evolve their networks to support advanced
`services such as video in a flexible way, with a singular solution for both short-loop and
`long-loop applications. It will include all the feature and performance benefits of ADSL2
`while maintaining the capability to interoperate with legacy equipment. As such, carriers
`will be able to overlay new, advanced technologies without having to “forklift-upgrade”
`existing equipment, allowing for a gradual transition to advanced services.
`Rate and Reach Improvements
`ADSL2 has been specifically designed to improve the rate and reach of ADSL largely by
`achieving better performance on long lines in the presence of narrowband interference.
`ADSL2 achieves downstream and upstream data rates of about 12 Mbps and 1 Mbps
`respectively, depending on loop length and other factors. ADSL2 accomplishes this by
`improving modulation efficiency, reducing framing overhead, achieving higher coding
`gain, improving the initialization state machine, and providing enhanced signal
`processing algorithms. As a result, ADSL2 mandates higher performance for all
`standard-compliant devices.
`ADSL2 provides better modulation efficiency by mandating four-dimensional, 16-state
`trellis-coded and 1-bit quadrature amplitude modulation (QAM) constellations, which
`provide higher data rates on long lines where the signal-to-noise ratio (SNR) is low. In
`addition, receiver-determined tone reordering enables the receiver to spread out the
`non-stationary noise due to AM radio interference to get better coding gain from the
`Viterbi decoder.
`ADSL2 systems reduce framing overhead by providing a frame with a programmable
`number of overhead bits. Therefore, unlike the first-generation ADSL standards where
`the overhead bits per frame are fixed and consume 32 kbps of actual payload data, in
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`1 G.992.3, or G.dmt.bis is the standard for full-rate ADSL2. G.992.4, or G.lite.bis, is for G.lite.
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`Dish
`Exhibit 1047, Page 2
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`the ADSL2 standard the overhead bits per frame can be programmed from 4 to 32 kbps.
`In first-generation ADSL systems, on long lines where the data rate is low (e.g. 128
`kbps), a fixed 32 kbps (or 25% of the total data rate) is allocated to overhead
`information. In ADSL2 systems, the overhead data rate can be reduced to 4 kbps, which
`provides an additional 28 kbps for payload data.
`On long lines where data rates are lower, ADSL2 achieves higher coding gain from the
`Reed-Solomon (RS) code. This is due to improvements in the ADSL2 framers that
`improve flexibility and programmability in the construction of the RS codewords.
`Additionally, the initialization state machine has numerous improvements that provide
`increased data rates in ADSL2 systems. Examples include:
`• Power cutback capabilities at both ends of the line to reduce near-end echo and the
`overall crosstalk levels in the binder.
`• Determination of the pilot tone location by the receiver in order to avoid channel nulls
`from bridged taps or narrow band interference from AM radio.
`• Control of certain key initialization state lengths by the receiver and transmitter in
`order to allow optimum training of receiver and transmitter signal processing
`functions.
`• Determination of the carriers used for initialization messages by the receiver in order
`to avoid channel nulls from bridged taps or narrow band interference from AM radio.
`Improvement in channel identification for training receiver time domain equalizer with
`spectral shaping during Channel Discovery and Transceiver Training phases of
`initialization.
`• Tone blackout (disabling tones) during initialization to enable radio frequency
`interference (RFI) cancellation schemes.
`Figure 1 shows the rate and reach of ADSL2 as compared to the first-generation ADSL
`standard. On longer phone lines, ADSL2 will provide a data rate increase of 50 kbps for
`upstream and downstream; a significant increase for those customers who need it most.
`This data rate increase results in an increase in reach of about 600 feet, which translates
`to an increase in coverage area of about 6%, or 2.5 square miles.
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`Dish
`Exhibit 1047, Page 3
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`White Paper: ADSL2/ADSL2PLUS
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`Figure 1: ADSL2 systems can deliver an improvement in reach of about 600 feet.
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`Diagnostics
`Determining the cause of problems in consumer ADSL service has at times been a
`challenging obstacle in ADSL deployments. To tackle the problem, ADSL2 transceivers
`have been enhanced with extensive diagnostic capabilities. These diagnostic
`capabilities provide tools for trouble resolution during and after installation, performance
`monitoring while in service, and upgrade qualification.
`In order to diagnose and fix problems, ADSL2 transceivers provide for measurements of
`line noise, loop attenuation, and signal-to-noise ratio (SNR) at both ends of the line.
`These measurements can be collected using a special diagnostic testing mode even
`when line quality is too poor to actually complete the ADSL connection.
`Additionally, ADSL2 includes real-time performance monitoring capabilities that provide
`information on line quality and noise conditions at both ends of the line. This information
`is interpreted by software and then used by the service provider to monitor the quality of
`the ADSL connection and prevent future service failures. It can also be used to
`determine if a customer can be offered higher data rate services.
`Power Enhancements
`First-generation ADSL transceivers operate in full-power mode day and night, even
`when not in use. With several millions of deployed ADSL modems, a significant amount
`of electricity can be saved if the modems engage in a standby/sleep mode just like
`computers. This would also save power for ADSL transceivers operating in small
`remote units and digital loop carrier (DLC) cabinets that operate under very strict heat
`dissipation requirements (Figure 2). To address these concerns, the ADSL2 standard
`brings in two power management modes that help reduce overall power consumption
`while maintaining ADSL's "always-on" functionality for the user. These modes include:
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`Dish
`Exhibit 1047, Page 4
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`Figure 2: ADSL2's L2 power mode allows a broadband modem to quickly move from L2 to
`L0 operation and back without bit errors.
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`L2 low-power mode
`This mode enables statistical powers savings at the ADSL transceiver unit in the central
`office (ATU-C) by rapidly entering and exiting low power mode based on Internet traffic
`running over the ADSL connection.
`L3 low-power mode
`This mode enables overall power savings at both the ATUC and the remote ADSL
`transceiver unit (ATU-R) by entering into sleep mode when the connection is not being
`used for extended periods of time.
`The L2 power mode is one of the most important innovations of the ADSL2 standard.
`ADSL2 transceivers can enter and exit the L2 low power mode based on the Internet
`traffic over the ADSL connection. When large files are being downloaded, ADSL2
`operates in full power mode (called "L0" power mode) in order to maximize the download
`speed. When Internet traffic decreases, such as when a user is reading a long text
`page, ADSL2 systems can transition into L2 low power mode, in which the data rate is
`significantly decreased and overall power consumption is reduced.
`While in L2, the ADSL2 system can instantly re-enter L0 and increase to the maximum
`data rate as soon the user initiates a file download. The L2 entry/exit mechanisms and
`resulting data rate adaptations are accomplished without any service interruption or even
`a single bit error, and as such, are not noticed by the user.
`The L3 power mode is a sleep mode where no traffic can be communicated over the
`ADSL connection when the user is not online. When the user returns to go on-line the
`ADSL transceivers require approximately three seconds to re-initialize and enter into
`steady-state communication mode.
`Rate Adaptation
`Telephone wires are bundled together in multi-pair binders containing 25 or more twisted
`wire pairs. As a result, electrical signals from one pair can electro-magnetically couple
`onto adjacent pairs in the binder (Figure 3). This phenomenon is known as “crosstalk”
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`Dish
`Exhibit 1047, Page 5
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`and can impede ADSL data rate performance. As a result, changes in the crosstalk
`levels in the binder can cause an ADSL system to drop the connection. Crosstalk is just
`one reason that ADSL lines drop connections. Others include AM radio disturbers,
`temperature changes, and water in the binder.
`Figure 3: When adjacent pairs couple together they can cause crosstalk, potentially
`forcing the ADSL system to drop a connection.
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`ADSL2 addresses these problems by seamlessly adapting the data rate in real-time.
`This new innovation, called seamless rate adaptation (SRA), enables the ADSL2 system
`to change the data rate of the connection while in operation without any service
`interruption or bit errors. ADSL2 simply detects changes in the channel conditions—for
`example, a local AM radio station turning off its transmitter for the evening—and adapts
`the data rate to the new channel condition transparently to the user.
`SRA is based on the decoupling of the modulation layer and the framing layer in ADSL2
`systems. This decoupling enables the modulation layer to change the transmission data
`rate parameters without modifying parameters in the framing layer which would cause
`the modems to lose frame synchronization resulting in uncorrectable bit errors or system
`restart. SRA uses the sophisticated online reconfiguration (OLR) procedures of ADSL2
`systems to seamlessly change the data rate of the connection.
` The protocol used for SRA works as follows:
`1. The receiver monitors the SNR of the channel and determines that a data
`rate change is necessary to compensate for changes in channel conditions.
`2. The receiver sends a message to the transmitter to initiate a change in data
`rate. This message contains all necessary transmission parameters for
`transmitting at the new data rate. These parameters include the number of
`bits modulated and transmit power on each subchannel in ADSL multicarrier
`system.
`3. The transmitter sends a "Sync Flag" signal which is used as a marker to
`designate the exact time at which the new data rate and transmission
`parameters are to be used.
`4. The Sync Flag signal is detected by the receiver and both transmitter and
`receiver seamlessly and transparently transition to the data rate.
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`Dish
`Exhibit 1047, Page 6
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`Bonding For Higher Data Rates
`A common requirement among carriers is the ability to provide different service level
`agreements (SLAs) to different customers. Data rates to homes and businesses can be
`significantly increased by bonding multiple phone lines together. To enable bonding, the
`ADSL2 standards support the ATM Forum's inverse multiplexing for ATM (IMA) standard
`(af-phy-0086.001) developed for traditional ATM architectures. Through IMA, ADSL2
`chipsets can bind two or more copper pairs in an ADSL link. The result is far greater
`flexibility with downstream data rates (Figure 4).
`Figure 4: Several phone lines can be bonded to multiply data rates.
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`The IMA standard specifies a new sublayer that resides between the ADSL physical
`layer (PHY) and the ATM layer. At the transmitter side, this sublayer, called the IMA
`sublayer, takes in a single ATM stream from the ATM layer and distributes this stream to
`multiple ADSL PHYs. At the receiver side, the IMA sublayer takes in ATM cells from
`multiple ADSL PHYs and reconstructs the original ATM stream.
`The IMA sublayer specifies IMA framing, protocols and management functions that are
`used to perform these operations when the PHYs are lossy (bit errors), asynchronous,
`and have different delays. In order to work under these conditions, the IMA standard
`also requires modifications to some of the standard ADSL PHY functions such as the
`discarding of idle cells and errored cells at the receiver. ADSL2 includes an IMA
`operation mode to provide the necessary PHY modifications for IMA to work in
`combination with ADSL.
`Channelization and Channelized Voice over DSL (CVoDSL)
`ADSL2 provides the ability to split the bandwidth into different channels with different link
`characteristics for different applications. For example, ADSL2 enables simultaneous
`support of a voice application, which might have low latency but a higher error rate
`requirement, and a data application, which might have high latency but lower error rate
`requirement.
`ADSL2's channelization capability also provides support for Channelized Voice over DSL
`(CVoDSL), a method to transport derived lines of TDM voice traffic transparently over
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`Dish
`Exhibit 1047, Page 7
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`DSL bandwidths. CVoDSL reserves 64 kbps "channels" of DSL bandwidth (Figure 5) to
`deliver PCM DS0s from the DSL modem to the remote terminal or central office, much
`like regular POTS (plain old telephone service). The access equipment then transmits
`the voice DS0s directly to the circuit switch via PCM.
`Figure 5: CVoDSL dedicates channels of physical layer bandwidth to carry TDM voice
`lines.
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`Figure 6: CVoDSL does not packetize voice data
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`Some Additional Benefits
`ADSL2 provides several other important features in addition to the benefits described
`here:
`Improved interoperability: Clarifications and additions to the initialization state machine
`improve interoperability and provide better performance when connecting ADSL
`transceivers from different chip suppliers.
`Fast startup: ADSL2 provides a fast startup mode that reduces initialization time from
`more than 10 seconds (as is required for ADSL) to less than 3 seconds.
`All-Digital Mode: ADSL2 enables an optional mode that allows for transmission of ADSL
`data in the voice bandwidth, adding 256 kbps of upstream data rate. This is an attractive
`option for businesses that have their voice and data services on different phone lines,
`and value the extra upstream bandwidth.
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`Dish
`Exhibit 1047, Page 8
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`Support of Packet-Based Services: ADSL2 includes a packet mode transmission trans-
`convergence layer (PTM-TC) that enables packet- based service (such as Ethernet) to
`be transported over ADSL2.
`ADSL2plus
`ADSL2plus reached consent at the ITU in January 2003, joining the ADSL2 standards
`family as G.992.5. The ADSL2plus recommendation doubles the downstream
`bandwidth, thereby increasing the downstream data rate on telephone lines shorter than
`about 5,000 feet.
`While the first two members of the ADSL2 standards family specify a downstream
`frequency band up to 1.1 MHz and 552 kHz respectively, ADSL2plus specifies a
`downstream frequency up to 2.2 MHz (Figure 7). The result is a significant increase in
`downstream data rates on shorter phone lines (Figure 8). ADSL2plus upstream data
`rate is about 1 Mbps, depending on loop conditions.
`Figure 7: ADSL2plus doubles the bandwidth used to carry downstream data.
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`Figure 8: ADSL2plus doubles the maximum downstream data rate.
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`Dish
`Exhibit 1047, Page 9
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`White Paper: ADSL2/ADSL2PLUS
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`Page 2
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`ADSL2plus can also be used to reduce crosstalk. ADSL2plus provides the capability to
`use only tones between 1.1 MHz and 2.2 MHz by masking the downstream frequencies
`below 1.1 MHz. This can be particularly useful when ADSL services from both the
`central office (CO) and a remote terminal (RT) are present in the same binder as they
`approach customers' homes (Figure 9). The crosstalk from the ADSL services from the
`RT onto the lines from the CO can significantly impair data rates on the line from the CO.
`Figure 9: ADSL2plus can be used to reduce crosstalk.
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`ADSL2plus can correct this problem by using frequencies below 1.1 MHz from the
`central office to the remote terminal, and frequencies between 1.1 MHz and 2.2 MHz
`from the remote terminal to the customer premise. This will eliminate most of the
`crosstalk between the services and preserve data rates on the line from the central
`office.
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`Dish
`Exhibit 1047, Page 10