[ TECHNOLOGY OPPORTUNITY 2003-007]

Adaptive Wireless Modems for Multimedia Data

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Researchers at Queen’s University are developing a wireless adaptive modem with increased reliability and power efficiency. The main application of this project is the incorporation of a cost-effective (firmware-based) and backwards compatible adaptive mapping assignment in wireless modem devices that employ fixed modulation constellations (hardwired into widely used chipsets) for the transmission of heterogenous multimedia data. Hence, as different types of data arrive for transmission at the modem, it adapts to the new data by simply selecting (via a software operation) the appropriate mapping. Such technology, which can be implemented in existing modems without changing hardware design, has high potential for the rapidly growing markets in wireless services over the Internet, telecommunications networks and cable networks.

Background:
Digitized multimedia data sources (such as image, video, text and speech signals) contain substantial amounts of natural redundancy in the form of non-uniformity and memory. In other words, uncompressed multimedia files contain strongly uneven amounts of “zeros” and “ones” in their binary format. Furthermore, even when they are compressed, they still exhibit short and long term residual redundancy due to the suboptimality of the compression algorithm (see Figure 1).

In the design of the existing modem technology, it is universally assumed that the data bits at the input of the modulator are equally likely. This assumption justifies the widespread use of fixed signal mappings (e.g., the so-called Gray mapping) which take the bits in the input stream and map them to modulation symbols. However, such fixed mappings, designed for uniform sources, in reality may allow symbols that are highly frequent (on both local and global time scales) to be transmitted at high power relative to infrequent symbols, resulting in significant power inefficiencies. Current modems employ a static mapping in the sense that any given sequence of input bits is always mapped to and transmitted by the same modulation signal.



Figure 1: Local non-uniformity in a compressed AVI (video) file
measured in proportion of zeros per 600-bit block.

Description:
Given the redundancy in the form of non-uniformity inherent in multimedia sources (both uncompressed and compressed), researchers at Queen’s University are developing a wireless adaptive modem with increased reliability and power efficiency. The main application of this project is the incorporation of a cost-effective (firmware-based) and backwards compatible adaptive mapping assignment in wireless modem devices that employ fixed modulation constellations (hardwired into widely used chipsets) for the transmission of heterogenous multimedia data. Hence, as different types of data arrive for transmission at the modem, it adapts to the new data by simply selecting (via a software operation) the appropriate mapping. Such technology, which can be implemented in existing modems without changing hardware design, has high potential for the rapidly growing markets in wireless services over the Internet, telecommunications networks and cable networks.

Status of Development:
Queen’s Researchers have designed novel signal mappings for the modulation and transmission of data sources with non-uniformity, and simple modulation algorithms to adaptively switch between mappings according to the short-term non-uniformity characteristics of the data source. The researchers intend to explore both further refinements and extensions through simulation (software prototype) and to construct a physical prototype.

Benefits:
In experiments involving multimedia data, Queen’s researchers have observed typical gains over the Gray mapping of 1 dB for compressed AVI (video) files and 6 dB for uncompressed facsimile documents using 64-ary Quadrature Amplitude Modulation (QAM). In wireless communications, where bandwidth, power and/or delay constraints are stringent, performance gains as little as 0.5 dB are considerable.


Status of Commercialization:
PARTEQ Innovations, the technology transfer office of Queen’s University, is seeking industrial partners willing to support on-going development of the product and/or who are interested in licensing the intellectual property. Patent applications are currently pending.

Contact:
Randall North
Associate Director, Commercial Development
Phone: (613) 533-2342
FAX: (613) 533-6853
E-mail: rnorth@parteqinnovations.com
Ref: Tech ID 2003-007