DS-UWB vs. 802.11n: What’s the Best Connectivity Option?

According to Freescale guy Matt Wellborn, UWB is faster, cheaper, and less power-hungry than 802.11n:

Current proposals for scaling 802.11 systems to higher rates (500 Mbits/s or more) in 802.11n are based on the continued use of 64-QAM. Scaling to higher rates will be enabled through the use of multiple-input-multiple-output (MIMO) techniques that use multiple antennas to send multiple data streams in parallel through the wireless channel. For this approach, the processing complexity also increases with data rate (FEC decode, FFT/iFFT, equalization, etc). There will also be increased complexity and power consumption due to the requirement for up to 4 transmit/receive processing chains (multiple ADC/DAC pairs, filters, amplifiers, etc).

As digital process technology scales, the digital portions of each system will scale much faster to lower cost and power. The significant analog potions of the system will scale more slowly and will thus have a proportionally bigger impact when these functions represent a larger portion of the implementation. The power consumption and area required for large ADCs and linear PAs becomes a bigger factor as digital technology scales in the future.

As we evaluate the two technologies for very high rate, low power applications, we see that the impact of system bandwidth is significant in many areas. As the narrowband designs are extended to higher rates, the use of high order modulation and multiple-antenna technologies can provide scalable and robust performance, but will also likely lead to increased complexity and power consumption. Systems that use wider bandwidths, such as DS-UWB, can use fundamentally different design approaches to provide wireless connectivity solutions that scale to even higher data rates with more scalable and lower complexity implementations.

Is he right?

3 thoughts on “DS-UWB vs. 802.11n: What’s the Best Connectivity Option?”

  1. Actually, no. You have to evaluate what the technologies actually do. 802.11n is meant to go a longer ratnge than UWB, which is inherently limited in power and by its inability to exploit spatial diversity. You are trading off complexity for range and and increasing complexity and consumed power. However, it’s nonsense to say the transmit powers scale linearly: they don’t, because exploitation of spatial diversity means that for the same power as a SISO system you get higher throughput (provided the channels are not pathological). Nor does the number of coders necessarily increase.

    There are ways to scale the complexity in other ways that aren’t burdensome, although I plead ignorance on the exact tradeoffs, but suffice it to say you can run hardware N times as fast and get complexity reduced by up to 1/N where N is the number of channels, with only added sampling converters. You pay for that, of course, but it’s a designer’s choice.

    It all goes back to what some professor said in CA a few years ago; with some adjustment of the numbers: If I promise to give you 1 Gbps at a range of 100Km for 1 Dollar, I’m lying to you.

    So it’s -again- not an either/or choice of UWB vs. 802.11n, but rather a choice of really high data rates with lower complexity and low range (and “often” more consumed power) vs. almost as really high data rates with higher complexity and significantly longer range.

    There’s one other thing that this guy doesn’t want to admit: by using an MBOA core and 802.11n, you have the potential to integrate both technologies on a single radio. He can’t do that as well.

  2. I should note one other thing there: transmitted power- the power you put out over the air- is the biggest item in a consumed power budget, even for these radios.

  3. Yes, but in a MIMO system receives take an awful lot of power too, which some say makes them unsuitable for mobile (battery-powered) applications. We may be coming to a fork in the road for home networking where the fixed infrastructure is going to use some sort of PLC or Ethernet and we’ll only use wireless for truly mobile appplications, and most of it will be UWB. But that’s a few years away, most likely, as consumers aren’t acutely aware of limitations of a/b/g and naively think n will solve any issues they have with no loss of battery life. If only.

    I like that dual-mode radio, though.

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