Next Generation Copper Bonding Technology: MIMO-on-DMT
Positron leverages a combination of both MIMO (Multi-Input-Multi-Output) techniques and Discrete Multi-tone (DMT) as the foundation for its copper bonding technology, which provides unparalleled performance as compared to legacy HDSL and E.SHDSL copper bonding technologies. By performing bonding at the physical layer, Positron’s Aktino technology overcomes the problems of existing bonding methods and enables the delivery of high quality, high bandwidth broadband services network-wide.
Key advantages of Positron's next generation copper bonding technology:
- Provides up to 100 Mbps to 12 Kft/3.7 Km
- Requires only one-third to one-half the number of pairs required by legacy bonding technologies like HDSL or E.SHDSL to deliver the same bandwidth
- Reaches two to four times more customers which ensures delivery of services network-wide
- Provides high immunity to noise and line impairments which ensures fiber-like reliability even in harsh environments
- Provides fast recovery from pair failures or temporary outages
- Compatible with Dynamic Spectral Management used to optimize ADSL performance from DSLAMs
- Fully T1.417 compliant DMT line code with industry standard tone spacing and symbol rates
All these advantages translate into increased rate, reach and reliability that enable providers to leverage their existing copper infrastructure to quickly provide profitable and lasting broadband services.
MIMO Mitigates Interference
Crosstalk is the limiting factor for all DSL transmission and it determines the true rate and reach of any DSL line. However, MIMO techniques have had a major impact in removing or canceling crosstalk. By treating the groups of bundled copper pairs (called “binder groups”, typically consisting of 25 to 100 pairs per group) as a multiple-input/multiple-output channel and creating a transceiver which treats multiple pairs together, it is possible to separate crosstalk from signal. The MIMO transceiver performs joint signal processing across all the pairs it controls and creates a mathematical picture of the crosstalk environment which those pairs inhabit. The mathematical picture is constantly recalculated and updated to ensure that the best possible decision is made using this information. Transmission rates can be increased by factors of 2 times compared to today’s best DMT modem or 10 times compared to echo canceled legacy modems (HDSL, SHDSL). These are the kind of increases in performance that drive substantial economic benefits for providers and have defined the next generation of copper bonding technology.
DMT Provides Superior Spectral Compatibility and Supports Symmetric and Asymmetric Bandwidth
MIMO processing can theoretically be applied to any line code used in wireline transmission. Positron has chosen Discrete Multi-tone (DMT) as the foundation for its copper bonding technology for the following reasons:
- DMT, even without MIMO processing, is a superior line code that is most widely used in the wireline world as both ADSL2 and VDSL2.
- There are many kinds of impairments in wireline transmission including attenuation of the line, imperfections in the line (bridge taps and splices) and radiated interference (Ham radio transmissions and broadcast radio). However, one of the key attributes of DMT is its ability to work around narrow-band interference. When interference exists that can make a portion of the frequency spectrum unusable, a DMT system enables it to have complete and unimpaired use of the entire remaining portion of the frequency spectrum. With single carrier systems such as HDSL, SHDSL and QAM, the entire system performance is degraded and sometimes made unusable by a single narrow-band interferer.
- DMT systems provide superior spectral compatibility with ADSL and VDSL, which are DMT-based and immune to DMT generated cross-talk. When DMT is used in longer reach applications (greater than 5 Kft/1.5 Km of twisted copper pairs) and in a frequency division multiplexed format (FDM band separation is the most widely deployed method for full duplex operation in DMT systems), there is essentially no cross talk interference caused by similar DMT transceivers on neighboring transceivers. This eliminates the complexity and cost of echo-cancellation processing that other line codes like E.SHDSL use. For example, under heavy alien disturber scenarios, bonded ADSL2 can lose up to 50 percent of downstream and upstream bandwidth.