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Video Problem 6: Equalization Equalization issues are unavoidable when using CAT-5 cable. Since the cable attenuates some of the signal bandwidth, the high frequency signals will be distorted. This causes the smearing apparent in Figure 13. Compensation is needed to rectify the high frequency losses of the system. This compensation can be provided at the driver (before entering the cable, predistortion) or at the receiver (after going through the

M-BOK coding In addition to traditional source coding and channel coding techniques such as convolutional encoding and block interleaving (used to counter the detrimental effects of a long run of identical bits and of short duration fades), other coding opportunities exist as a result of spreading each bit over a large bandwidth with the use of wavelets.

First, each information bit is not necessarily associated with a single transmitted wavelet. A group of bits can be associated with one of a family of orthogonal, direct sequence codes. A train of successive wavelets is then transmitted, each having as its individual bi-polar modulation, the polarity of its associated chip” in the sequence.

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At the receiver, signal processing is used to determine which of the orthogonal, direct sequence codes was most likely to have been transmitted. With this approach, both the detrimental effects of short duration fades and long runs of identical bits are addressed.

Multi-band UWB For channel bonding ultra-wide band communications, two or more OFDM signals are used to transmit the high speed data stream from one source. Individual bits can be assigned to one of the 802.11a channels in blocks or individually, and concatenated coding techniques can be applied before and after the bit assignments.

All the DSP functions required in an OFDM channel such as interleaving, mapping, and IFFT are required for the transmitter, and the inverse functions for the receiver. Although this approach provides a much higher density of bits-per-hertz and a much reduced spectral bandwidth than direct sequence ultra-wide band, it is much more complicated in terms of RF and analog circuitry, with an associated higher cost.

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MBUWB requires designers to go back to traditional RF architectures, advanced synthesizer techniques, and all the difficulties associated with handling OFDM signals over a narrowband radio.

On the other hand MB-UWB minimizes some of the UWB challenges mentioned above such as ADC power consumption, wideband matching (and associated power dissipation), CW interference issues, difficulties in the generation and control of a wideband spectrum, achieving the very precise timing required, and handling a high speed complex digital baseband (although this last point is debatable).

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Unlike DS-UWB, MB-UWB benefits from the possibility of using a 1x over sampling ADC and DAC (1GS/s) to reduce power consumption while handling large signal interferers (which could be as high as 30dB). MB-UWB performance depends on the ability of designing a LO capable of being able to hop quickly (less than 10ns).

In summary, from a performance point of view, MB-UWB provides higher data throughput and faster acquisition time, interference avoidance (obtained by attenuating or not using particular sub-bands), and some flexibility through multiple access.

The process of filling the holes identified by the full range of coverage metrics is the heart of the coverage-driven verification process. By definition, when 100% coverage across all metrics is achieved then the verification confidence should be high enough to tape out. SystemVerilog provides cover properties for lower-level coverage points, cover groups for tracking higher-level values, and support for cross-coverage.

The VMM for SystemVerilog discusses how different approaches may be used at different points in the process to improve coverage. Figure 2 takes the constrained-random verification process graph line from Figure 1 and expands it to show more detail.

The first part of the process entails setting up the testbench environment. Generally no chip-level or system-level testing is possible until this environment is established. However, if designers are coding RTL in parallel they may be running block-level directed tests or formal analysis during this period.

Once the verification environment is ready, the development team can start to run constrained-random tests and hit the first set of coverage points. At this point the tests are typically quite broad, generating a wide range of behavior for the design.

Although, flash-based headsets offer software upgrades allowing them to operate with new phones, extensive interoperability testing means that for high-volume production ROM-based devices are far more common, translating into lower production costs.

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