Finally unplugged: Wireless digital video (WiDV)
With recent advances in wireless technology, multiple markets are beginning to see new wireless digital video applications emerge.
There are a number of ways to get video from a transmitter to the screen on your cell phone. This article examines the alternatives, the challenges, and the tradeoffs
With recent advances in wireless technology, multiple markets are beginning to see new wireless digital video applications emerge. These markets include personal computers, consumer electronics (CE) and home entertainment, and mobile devices. There are many applications in these markets that are ideal for wireless video communications and the convenience and mobility that it affords. This is an important step in the evolution of wireless communications.
Up until recently, wireless communications has struggled to gain wide traction in video applications. The challenges to date have included issues such as bandwidth availability and quality-of-service requirements, rendering the existing offerings large, expensive, and power-hungry. In recent years, however, the emergence of the ultrawideband (UWB) spectrum, with its short range and high bandwidth (greater than 1 Gbit/sec) characteristics, make it ideal for in-room wireless distribution of video. It’s not just additional bandwidth that is required, however. While available bandwidth is a significant part of the solution, efficient algorithms that optimize the use of that bandwidth are also very important.
This article will evaluate several applications across various market segments and will compare the various technologies and their applicability to those applications.
As we evaluate the applications of wireless digital video across the various market segments we find that there is extensive overlap. As shown in Figure 1, devices such as ultramobile PCs and PDAs are used extensively in both the PC and mobile environments. Game consoles are used in both the PC and CE space. A DVD player is an example of a device that overlaps all three markets.
Because of the overlap, the ideal wireless digital video technology must address the needs of all three of these markets.
PC applications. One of the most prolific video devices is the liquid-crystal display (LCD) for the PC. Many of us use one at home and a second one at work. We start the morning typically by “unplugging” our notebook PC from our monitor and other peripheral devices at home. Then, when we get to work, we plug it back into our monitor and peripherals or docking station there. At the end of the day, we reverse that cycle. For many of us, the cycle continues between the office and conference room where we plug our notebooks into projectors.
Notebook PCs would finally be truly mobile if they no longer required you to “plug in” to a display device such as a monitor or projector. A wireless docking station is one of the first products available to PC users enabling such ease of use. Following the wireless docking station will be wireless capability embedded into projectors and LCDs. Inevitably, video cables and wired connections will be relegated to the past.
The PC segment is the most challenging for wireless digital video. This market demands not only high-quality wireless display of movies but also the ability to handle the unique challenges that graphics and text introduce, which are distinct and different from playing a DVD.
Wireless communication of high-quality graphics and text is next to impossible with traditional MPEG or motion JPEG approaches because of the level of compression and the artifacts that compression introduces. Graphics move from a graphics processor to a display in an uncompressed form. To achieve high-quality graphics from a wireless link requires significantly more bandwidth (raw SXGA data rate is greater than 1.8 Gbits/sec) that has either not been available or not optimally utilized. That’s because traditional compression approaches such as MPEG were developed specifically for natural image video compressed for DVD or satellite broadcasting over a narrow 5- to 20-Mbit/sec data pipe, and not for high-resolution graphics. So, for PC applications, a new capability that optimizes the use of the available bandwidth afforded by the UWB spectrum is required that also accounts for wireless display of text and graphics.
In a wireless docking scenario, attaching to an LCD monitor is not the only requirement. Additionally, a user will require wireless access to all of the usual peripherals including network, audio, printers, and others. The new approach has the added benefit of simultaneously operating with Certified Wireless USB, which ensures interoperability with USB peripherals that may be attached to the docking station. The demand for wireless connectivity to external displays will grow further as mobile PCs such as the ultramobile PC and tablet PC become more mainstream and users seek ways to wirelessly export the content to larger displays.
Consumer electronics and home entertainment applications. Ease of installation and movement will excite consumers who adopt wireless digital video in the home. Construction costs to hard-wire video connections between high-definition TVs (HDTVs) and projectors to set-top boxes, DVD players, and game consoles using expensive HDMI cables can easily approach hundreds of dollars. Sometimes these cables can cost more than the audio/video (A/V) components they are connected to. Coupled with the flexibility to locate A/V equipment where it is convenient and more visually appealing, wireless video is an ideal technology for home entertainment applications.
With the new approach to wireless video, traditional PC segment products can also seamlessly integrate with the home A/V environment. For example, visiting friends can play their game console, iPod, or PC-based video content through an existing home setup designed around wireless video.
Mobile applications. Wireless digital video in the mobile space will span the PC, CE, and mobile phone segments. As notebooks continue the trend to become smaller and smaller and mobile phones are enhanced to perform additional functions that are done by those PCs today, the desire to wirelessly attach to an external monitor will grow. The scenario of using a mobile phone to drive presentations to a projector is already being demonstrated in TV commercials today.
Smart phones are incorporating more PC functions, such as word processing and spreadsheets. These capabilities naturally need to be displayed on large screens such as external monitors and projectors. Users will not only store presentations on these smart phones, but with the exception of having a large display and keyboard, they would provide all of the capabilities that their computers provide today. Adding the ability to output to an external display, keyboard, and mouse will give these smart phones the ability to perform many of the same functions available with home or office PCs. These devices will then have the same demands as the PC environment for high-quality graphics and text, reinforcing the need for a wireless digital video technology that is optimized to use the high bandwidth available by low-power UWB technology.
There are two basic approaches that wireless connectivity silicon vendors are using to wirelessly distribute digital video. There is an inadequate, high-compression approach that uses MPEG or motion JPEG. This approach was designed to distribute data through small pipes, so extremely high compression is required. Then there is the more optimized approach based on the WiMedia common radio platform, which uses more sophisticated compression algorithms that perfectly match the applied compression to use the available bandwidth. This approach provides a much better user experience with high-quality, low-latency video and graphics.
The high-compression approach has several characteristics that limit widespread adoption of true, high-quality wireless digital video.
Lower quality. Approaches such as MPEG and motion JPEG use compression algorithms that were developed for low-bandwidth (5- to 20-Mbit/sec) connections. Thirty to fifty times (30× to 50×) compression is required for most high-definition video for distribution using these algorithms (see Figure 2). At that compression level, this results in a picture of visibly lower quality, with significant artifacts and blurring. This represents a nonoptimal approach to the bandwidth afforded by UWB technology.
High cost and high latency. These compression techniques come with significant added cost because expensive encoder and decoder chips must be added to the overall solution. Depending on the video quality, there can be as many as two additional chips at each end of the solution, resulting in additional costs to an end-product manufacturer of up to $60 at each end. By the time the product reaches the consumer, that $60 becomes $300.
In addition to the encoder and decoder chips, memory chips buffering several frames introduce undesirable latency and increase system cost. All of this is because existing wired video approaches are being adapted to a narrow wireless data pipe instead of developing a solution that builds upon the unique advantages of UWB.
High power. Additional cost and latency are not the only issues when adding more components to a solution. Adding more chips also has a significant impact on power consumption. Power consumption is a very important issue when incorporating wireless digital video capability into battery-operated mobile devices.
Solution size. Solution size is always a consideration, especially in mobile technology. The adoption rate of many CE devices is directly correlated to the size and cost of the solution. The more chips that are included in the solution, the greater the likelihood of market failure.
Alternatively, UWB with its very large available bandwidth has opened the door for a new technology that optimizes quality, cost, size, and power by making great use of the available bandwidth. With the additional bandwidth, wireless digital video-or WiDV-is a new standard developed to address the compelling needs and capabilities for distribution of wireless digital video using UWB technology based on the WiMedia Common Radio Platform.
WiDV is WiQuest’s innovative technology that is the first to deliver wireless transmission of high-quality digital video for PC, CE, and mobile applications. Compared to other wireless video approaches, WiDV is unique in that it provides more efficient compression with fewer components to achieve a high-quality video or graphic image with a completely integrated wireless video solution (see Figure 3). WiDV results in the highest-quality, lowest-cost, lowest-latency, smallest-form-factor, and lowest-power-consumption wireless video solution on the market today. It not only enables wireless HDTV connectivity but also wireless PC graphics connections, where previous technologies have proved unacceptable.
WiDV technology was developed specifically to address the unique requirements of efficient video transmission using UWB wireless connections. In this regard, it represents the optimum solution for wireless digital video as an integrated system solution versus attempts at combining existing wired video standards with a radio. WiDV uses patent-pending innovations that enable a high-quality and efficient video transport over the WiMedia UWB wireless link. WiDV builds upon the WiMedia Common Radio Platform exactly like other protocols such as Wireless USB. It peacefully coexists with other protocols that are based on the WiMedia radio.
WiDV is a trademark of WiQuest Communications Inc.
Alun Roberts is vice president of marketing at WiQuest Communications (www.wiquest.com). He joined WiQuest from AMI Semiconductor Inc., where he was responsible for marketing strategy.
