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Optoelectronics/Displays??

Raise UWB throughput for wireless HD video

Posted: 01 Apr 2008 ?? ?Print Version ?Bookmark and Share

Keywords:wireless HD video? UWB? HDMI? USB?

The airlink delivered approximately 1.6Gbit/s at all antenna and device orientations and with humans and furniture blocking the beam. The display quality on the wired and wireless HDMI links was indistinguishable to the naked eye under all test conditions (Figure 3). The audio on both displays was synchronized with no perceptible delay indicating low latency on the UWB link.

Figure 3: Comparison of the video quality between the wired and wireless links revealed no visible differences under any of the test conditions, for any antenna orientation and with obstructions in the beam.

The video quality was tested with 2.4GHz Wi-Fi interference (streaming video from a website to a laptop) right next to the Radiospire device and with 900MHz interference from a nearby baby monitor. We have observed no degradation in video quality due to this interference.

We also verified the transmit power at the antenna port of the transmitter for FCC compliance (Figure 4). This was intended to be an informal verification.

Figure 4: Informal FCC compliance verificationConducted spectrum measurement at the antenna port of the transmitter. The average power at the antenna port is below -40 dBm/MHz and with some isotropic losses through the antenna meets the FCC limit.

Tables 2 and 3 summarize the tests we have performed and the test results.

 Table 2: Benchtop verification of the AirHook chipset
Table 2: Benchtop verification of the AirHook chipset

Table 3: System verification of the Radiospire AirHook chipset
Table 3: System verification of the Radiospire AirHook chipset

AirHook review
The Radiospire AirHook chipset implements a UWB point to point airlink with a transmitter on one end and a receiver on the other end. The chipset is composed of three devices on the TX end of the link and three counterpart devices on the RX end of the link (Table 4, Figure 5).

Table 4: Radiospire AirHook chipset
Table 4: Table 4: Radiospire AirHook chipset

Figure 5: Radiospire wireless HDMI solutionUWB TX and RX. The video interface supports almost any standard format including HDMI, DVI, XGA and analog video such as NTSC, composite and S-video.

The AirHook chipset employs OFDM signaling with 512 carriers using 16-QAM modulation. The spectrum of the RF signal is 1.7MHz wide, from 3.1- to 4.8GHz. The 6bit ADCs and DACs operate at 1.92GSps on an 850MHz baseband signal.

The Radiospire Baseband processor (Figure 6) incorporates low density parity check coding (LDPC) FEC functionalitya powerful FEC technology that significantly reduces bit error rate. While the raw airlink data rate reaches 2.2Gbit/s, the LDPC corrected data rate is 1.6Gbit/s, the throughput required for 1080p HD A/V transport.

Figure 6: Radiospire baseband processor was able to operate in either transmit or receive mode and interfacing between the video interface, such as the HDMI or the SVGA, and ADC or DAC chips.

The Radiospire ADC and DAC (Figure 7) have been segregated into their own 0.35?m SiGe BiCMOS ICs for optimum performance.

Figure 7: Radiospire ADC and DAC devices interfacing between the RF front end and the baseband processor

The Radiospire RF receiver and transmitter (Figures 8 and 9) have also been segregated into their own 0.35?m SiGe BiCMOS ICs to optimize signal integrity and bit error rate performance.

As evident from Figures 6 through 9, the clean segregation of the AirHook architecture and focused implementation of each functional block may explain why Radiospire has been able to reach 1.6 Gbit/s on their UWB interface.

Figure 8: Radiospire RF receiver device interfacing to the ADC

Figure 9: Radiospire RF transmitter device interfacing to the DAC

Conclusion
Following our recent EE Times UWB test, we were glad to discover that the throughput performance of UWB now has a new record of 1.6 Gbit/sperformance verified for the Radiospire AirHook chipset.

This is a significant step up from the 675Mbit/s PHY rate of Pulse-LINK's CWave, the winner of our last test and much higher than WiMedia, which delivered around 50 Mbit/s at the CW-USB application layer and now promises around 160Mbit/s with the next generation products.

It is notable that the two highest performing UWB chipsets available today are not based on the WiMedia standard and exceed the verified and expected WiMedia performance by an order of magnitude.

Radiospire is the first to enable uncompressed 1080p HD video transport in the UWB band at a level of throughput that seemed unreachable just a short while ago. While Radiospire's technology can be adapted to the emerging standards based 60GHz band, the UWB solution is the only working solution on the market today.

Radiospire's robust performance at a variety of antenna orientations, in the presence of interference and through obstructions will enable solid and successful UWB based products.

About the author
Fanny Mlinarsky
is the president of octoScope, a consulting firm focusing on architecture and performance of wireless data communications systems.


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